Link Cards to Accounts with proper relationship

Model Changes:
- Add Card.AccountId (nullable FK to Account)
- Add Card.Nickname field for friendly names
- Add Card.DisplayLabel computed property
- Add Account.Cards navigation property
- Add Account.DisplayLabel computed property

DbContext Updates:
- Configure Card → Account relationship (optional, restrict delete)
- Add index on Card.AccountId
- Set Card.Owner as required

Migration:
- Add LinkCardsToAccounts migration
- Adds AccountId and Nickname columns to Cards table
- Creates FK constraint from Cards to Accounts

This properly models the real-world relationship where payment cards
are linked to bank accounts (e.g., a Visa card draws from a checking
account, or a credit card is paid from a savings account).

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

MoneyMap/Data/MoneyMapContext.cs

@@ -27,8 +27,18 @@ namespace MoneyMap.Data
             {
                 e.Property(x => x.Issuer).HasMaxLength(100).IsRequired();
                 e.Property(x => x.Last4).HasMaxLength(4).IsRequired();
-                e.Property(x => x.Owner).HasMaxLength(100);
+                e.Property(x => x.Owner).HasMaxLength(100).IsRequired();
+                e.Property(x => x.Nickname).HasMaxLength(50);
+
+                // Card can be linked to an account (optional - for credit cards without linked account)
+                e.HasOne(x => x.Account)
+                 .WithMany(a => a.Cards)
+                 .HasForeignKey(x => x.AccountId)
+                 .OnDelete(DeleteBehavior.Restrict)
+                 .IsRequired(false);
+
                 e.HasIndex(x => new { x.Issuer, x.Last4, x.Owner });
+                e.HasIndex(x => x.AccountId);
             });
 
             // ---------- ACCOUNT ----------

MoneyMap/Migrations/20251010025545_LinkCardsToAccounts.Designer.cs

@@ -0,0 +1,528 @@
+// <auto-generated />
+using System;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Infrastructure;
+using Microsoft.EntityFrameworkCore.Metadata;
+using Microsoft.EntityFrameworkCore.Migrations;
+using Microsoft.EntityFrameworkCore.Storage.ValueConversion;
+using MoneyMap.Data;
+
+#nullable disable
+
+namespace MoneyMap.Migrations
+{
+    [DbContext(typeof(MoneyMapContext))]
+    [Migration("20251010025545_LinkCardsToAccounts")]
+    partial class LinkCardsToAccounts
+    {
+        /// <inheritdoc />
+        protected override void BuildTargetModel(ModelBuilder modelBuilder)
+        {
+#pragma warning disable 612, 618
+            modelBuilder
+                .HasAnnotation("ProductVersion", "9.0.9")
+                .HasAnnotation("Relational:MaxIdentifierLength", 128);
+
+            SqlServerModelBuilderExtensions.UseIdentityColumns(modelBuilder);
+
+            modelBuilder.Entity("MoneyMap.Models.Account", b =>
+                {
+                    b.Property<int>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("int");
+
+                    SqlServerPropertyBuilderExtensions.UseIdentityColumn(b.Property<int>("Id"));
+
+                    b.Property<int>("AccountType")
+                        .HasColumnType("int");
+
+                    b.Property<string>("Institution")
+                        .IsRequired()
+                        .HasMaxLength(100)
+                        .HasColumnType("nvarchar(100)");
+
+                    b.Property<string>("Last4")
+                        .IsRequired()
+                        .HasMaxLength(4)
+                        .HasColumnType("nvarchar(4)");
+
+                    b.Property<string>("Nickname")
+                        .HasMaxLength(50)
+                        .HasColumnType("nvarchar(50)");
+
+                    b.Property<string>("Owner")
+                        .IsRequired()
+                        .HasMaxLength(100)
+                        .HasColumnType("nvarchar(100)");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("Institution", "Last4", "Owner");
+
+                    b.ToTable("Accounts");
+                });
+
+            modelBuilder.Entity("MoneyMap.Models.Card", b =>
+                {
+                    b.Property<int>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("int");
+
+                    SqlServerPropertyBuilderExtensions.UseIdentityColumn(b.Property<int>("Id"));
+
+                    b.Property<int?>("AccountId")
+                        .HasColumnType("int");
+
+                    b.Property<string>("Issuer")
+                        .IsRequired()
+                        .HasMaxLength(100)
+                        .HasColumnType("nvarchar(100)");
+
+                    b.Property<string>("Last4")
+                        .IsRequired()
+                        .HasMaxLength(4)
+                        .HasColumnType("nvarchar(4)");
+
+                    b.Property<string>("Nickname")
+                        .HasMaxLength(50)
+                        .HasColumnType("nvarchar(50)");
+
+                    b.Property<string>("Owner")
+                        .IsRequired()
+                        .HasMaxLength(100)
+                        .HasColumnType("nvarchar(100)");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("AccountId");
+
+                    b.HasIndex("Issuer", "Last4", "Owner");
+
+                    b.ToTable("Cards");
+                });
+
+            modelBuilder.Entity("MoneyMap.Models.Receipt", b =>
+                {
+                    b.Property<long>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("bigint");
+
+                    SqlServerPropertyBuilderExtensions.UseIdentityColumn(b.Property<long>("Id"));
+
+                    b.Property<string>("ContentType")
+                        .IsRequired()
+                        .ValueGeneratedOnAdd()
+                        .HasMaxLength(100)
+                        .HasColumnType("nvarchar(100)")
+                        .HasDefaultValue("application/octet-stream");
+
+                    b.Property<string>("Currency")
+                        .HasMaxLength(8)
+                        .HasColumnType("nvarchar(8)");
+
+                    b.Property<string>("FileHashSha256")
+                        .IsRequired()
+                        .HasMaxLength(64)
+                        .HasColumnType("nvarchar(64)");
+
+                    b.Property<string>("FileName")
+                        .IsRequired()
+                        .HasMaxLength(260)
+                        .HasColumnType("nvarchar(260)");
+
+                    b.Property<long>("FileSizeBytes")
+                        .HasColumnType("bigint");
+
+                    b.Property<string>("Merchant")
+                        .HasMaxLength(200)
+                        .HasColumnType("nvarchar(200)");
+
+                    b.Property<DateTime?>("ReceiptDate")
+                        .HasColumnType("datetime2");
+
+                    b.Property<string>("StoragePath")
+                        .IsRequired()
+                        .HasMaxLength(1024)
+                        .HasColumnType("nvarchar(1024)");
+
+                    b.Property<decimal?>("Subtotal")
+                        .HasColumnType("decimal(18,2)");
+
+                    b.Property<decimal?>("Tax")
+                        .HasColumnType("decimal(18,2)");
+
+                    b.Property<decimal?>("Total")
+                        .HasColumnType("decimal(18,2)");
+
+                    b.Property<long>("TransactionId")
+                        .HasColumnType("bigint");
+
+                    b.Property<DateTime>("UploadedAtUtc")
+                        .HasColumnType("datetime2");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("TransactionId", "FileHashSha256")
+                        .IsUnique();
+
+                    b.ToTable("Receipts");
+                });
+
+            modelBuilder.Entity("MoneyMap.Models.ReceiptLineItem", b =>
+                {
+                    b.Property<long>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("bigint");
+
+                    SqlServerPropertyBuilderExtensions.UseIdentityColumn(b.Property<long>("Id"));
+
+                    b.Property<string>("Category")
+                        .HasMaxLength(100)
+                        .HasColumnType("nvarchar(100)");
+
+                    b.Property<string>("Description")
+                        .IsRequired()
+                        .HasMaxLength(300)
+                        .HasColumnType("nvarchar(300)");
+
+                    b.Property<int>("LineNumber")
+                        .HasColumnType("int");
+
+                    b.Property<decimal?>("LineTotal")
+                        .HasColumnType("decimal(18,2)");
+
+                    b.Property<decimal?>("Quantity")
+                        .HasColumnType("decimal(18,4)");
+
+                    b.Property<long>("ReceiptId")
+                        .HasColumnType("bigint");
+
+                    b.Property<string>("Sku")
+                        .HasMaxLength(64)
+                        .HasColumnType("nvarchar(64)");
+
+                    b.Property<string>("Unit")
+                        .HasMaxLength(16)
+                        .HasColumnType("nvarchar(16)");
+
+                    b.Property<decimal?>("UnitPrice")
+                        .HasColumnType("decimal(18,4)");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("ReceiptId", "LineNumber");
+
+                    b.ToTable("ReceiptLineItems");
+                });
+
+            modelBuilder.Entity("MoneyMap.Models.ReceiptParseLog", b =>
+                {
+                    b.Property<long>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("bigint");
+
+                    SqlServerPropertyBuilderExtensions.UseIdentityColumn(b.Property<long>("Id"));
+
+                    b.Property<DateTime?>("CompletedAtUtc")
+                        .HasColumnType("datetime2");
+
+                    b.Property<decimal?>("Confidence")
+                        .HasColumnType("decimal(5,4)");
+
+                    b.Property<string>("Error")
+                        .HasColumnType("nvarchar(max)");
+
+                    b.Property<string>("ExtractedTextPath")
+                        .HasMaxLength(1024)
+                        .HasColumnType("nvarchar(1024)");
+
+                    b.Property<string>("Model")
+                        .IsRequired()
+                        .HasMaxLength(100)
+                        .HasColumnType("nvarchar(100)");
+
+                    b.Property<string>("Provider")
+                        .IsRequired()
+                        .HasMaxLength(50)
+                        .HasColumnType("nvarchar(50)");
+
+                    b.Property<string>("ProviderJobId")
+                        .HasMaxLength(100)
+                        .HasColumnType("nvarchar(100)");
+
+                    b.Property<string>("RawProviderPayloadJson")
+                        .IsRequired()
+                        .HasColumnType("nvarchar(max)");
+
+                    b.Property<long>("ReceiptId")
+                        .HasColumnType("bigint");
+
+                    b.Property<DateTime>("StartedAtUtc")
+                        .HasColumnType("datetime2");
+
+                    b.Property<bool>("Success")
+                        .HasColumnType("bit");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("ReceiptId", "StartedAtUtc");
+
+                    b.ToTable("ReceiptParseLogs");
+                });
+
+            modelBuilder.Entity("MoneyMap.Models.Transaction", b =>
+                {
+                    b.Property<long>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("bigint");
+
+                    SqlServerPropertyBuilderExtensions.UseIdentityColumn(b.Property<long>("Id"));
+
+                    b.Property<int?>("AccountId")
+                        .HasColumnType("int");
+
+                    b.Property<decimal>("Amount")
+                        .HasColumnType("decimal(18,2)");
+
+                    b.Property<int?>("CardId")
+                        .HasColumnType("int");
+
+                    b.Property<string>("Category")
+                        .IsRequired()
+                        .HasMaxLength(100)
+                        .HasColumnType("nvarchar(100)");
+
+                    b.Property<DateTime>("Date")
+                        .HasColumnType("datetime2");
+
+                    b.Property<string>("Last4")
+                        .HasMaxLength(4)
+                        .HasColumnType("nvarchar(4)");
+
+                    b.Property<string>("Memo")
+                        .IsRequired()
+                        .ValueGeneratedOnAdd()
+                        .HasMaxLength(500)
+                        .HasColumnType("nvarchar(500)")
+                        .HasDefaultValue("");
+
+                    b.Property<string>("Name")
+                        .IsRequired()
+                        .HasMaxLength(200)
+                        .HasColumnType("nvarchar(200)");
+
+                    b.Property<string>("Notes")
+                        .IsRequired()
+                        .HasColumnType("nvarchar(max)");
+
+                    b.Property<string>("TransactionType")
+                        .IsRequired()
+                        .HasMaxLength(20)
+                        .HasColumnType("nvarchar(20)");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("AccountId");
+
+                    b.HasIndex("Amount");
+
+                    b.HasIndex("CardId");
+
+                    b.HasIndex("Category");
+
+                    b.HasIndex("Date");
+
+                    b.HasIndex("Date", "Amount", "Name", "Memo", "CardId", "AccountId")
+                        .IsUnique()
+                        .HasFilter("[CardId] IS NOT NULL AND [AccountId] IS NOT NULL");
+
+                    b.ToTable("Transactions");
+                });
+
+            modelBuilder.Entity("MoneyMap.Models.Transfer", b =>
+                {
+                    b.Property<long>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("bigint");
+
+                    SqlServerPropertyBuilderExtensions.UseIdentityColumn(b.Property<long>("Id"));
+
+                    b.Property<decimal>("Amount")
+                        .HasColumnType("decimal(18,2)");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("datetime2");
+
+                    b.Property<DateTime>("Date")
+                        .HasColumnType("datetime2");
+
+                    b.Property<string>("Description")
+                        .IsRequired()
+                        .HasMaxLength(500)
+                        .HasColumnType("nvarchar(500)");
+
+                    b.Property<int?>("DestinationAccountId")
+                        .HasColumnType("int");
+
+                    b.Property<string>("Notes")
+                        .IsRequired()
+                        .HasColumnType("nvarchar(max)");
+
+                    b.Property<long?>("OriginalTransactionId")
+                        .HasColumnType("bigint");
+
+                    b.Property<int?>("SourceAccountId")
+                        .HasColumnType("int");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("Date");
+
+                    b.HasIndex("DestinationAccountId");
+
+                    b.HasIndex("OriginalTransactionId");
+
+                    b.HasIndex("SourceAccountId");
+
+                    b.ToTable("Transfers");
+                });
+
+            modelBuilder.Entity("MoneyMap.Services.CategoryMapping", b =>
+                {
+                    b.Property<int>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("int");
+
+                    SqlServerPropertyBuilderExtensions.UseIdentityColumn(b.Property<int>("Id"));
+
+                    b.Property<string>("Category")
+                        .IsRequired()
+                        .HasColumnType("nvarchar(max)");
+
+                    b.Property<string>("Pattern")
+                        .IsRequired()
+                        .HasColumnType("nvarchar(max)");
+
+                    b.Property<int>("Priority")
+                        .HasColumnType("int");
+
+                    b.HasKey("Id");
+
+                    b.ToTable("CategoryMappings");
+                });
+
+            modelBuilder.Entity("MoneyMap.Models.Card", b =>
+                {
+                    b.HasOne("MoneyMap.Models.Account", "Account")
+                        .WithMany("Cards")
+                        .HasForeignKey("AccountId")
+                        .OnDelete(DeleteBehavior.Restrict);
+
+                    b.Navigation("Account");
+                });
+
+            modelBuilder.Entity("MoneyMap.Models.Receipt", b =>
+                {
+                    b.HasOne("MoneyMap.Models.Transaction", "Transaction")
+                        .WithMany("Receipts")
+                        .HasForeignKey("TransactionId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("Transaction");
+                });
+
+            modelBuilder.Entity("MoneyMap.Models.ReceiptLineItem", b =>
+                {
+                    b.HasOne("MoneyMap.Models.Receipt", "Receipt")
+                        .WithMany("LineItems")
+                        .HasForeignKey("ReceiptId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("Receipt");
+                });
+
+            modelBuilder.Entity("MoneyMap.Models.ReceiptParseLog", b =>
+                {
+                    b.HasOne("MoneyMap.Models.Receipt", "Receipt")
+                        .WithMany("ParseLogs")
+                        .HasForeignKey("ReceiptId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("Receipt");
+                });
+
+            modelBuilder.Entity("MoneyMap.Models.Transaction", b =>
+                {
+                    b.HasOne("MoneyMap.Models.Account", "Account")
+                        .WithMany("Transactions")
+                        .HasForeignKey("AccountId")
+                        .OnDelete(DeleteBehavior.Restrict);
+
+                    b.HasOne("MoneyMap.Models.Card", "Card")
+                        .WithMany("Transactions")
+                        .HasForeignKey("CardId")
+                        .OnDelete(DeleteBehavior.Restrict);
+
+                    b.Navigation("Account");
+
+                    b.Navigation("Card");
+                });
+
+            modelBuilder.Entity("MoneyMap.Models.Transfer", b =>
+                {
+                    b.HasOne("MoneyMap.Models.Account", "DestinationAccount")
+                        .WithMany("DestinationTransfers")
+                        .HasForeignKey("DestinationAccountId")
+                        .OnDelete(DeleteBehavior.Restrict);
+
+                    b.HasOne("MoneyMap.Models.Transaction", "OriginalTransaction")
+                        .WithMany()
+                        .HasForeignKey("OriginalTransactionId")
+                        .OnDelete(DeleteBehavior.SetNull);
+
+                    b.HasOne("MoneyMap.Models.Account", "SourceAccount")
+                        .WithMany("SourceTransfers")
+                        .HasForeignKey("SourceAccountId")
+                        .OnDelete(DeleteBehavior.Restrict);
+
+                    b.Navigation("DestinationAccount");
+
+                    b.Navigation("OriginalTransaction");
+
+                    b.Navigation("SourceAccount");
+                });
+
+            modelBuilder.Entity("MoneyMap.Models.Account", b =>
+                {
+                    b.Navigation("Cards");
+
+                    b.Navigation("DestinationTransfers");
+
+                    b.Navigation("SourceTransfers");
+
+                    b.Navigation("Transactions");
+                });
+
+            modelBuilder.Entity("MoneyMap.Models.Card", b =>
+                {
+                    b.Navigation("Transactions");
+                });
+
+            modelBuilder.Entity("MoneyMap.Models.Receipt", b =>
+                {
+                    b.Navigation("LineItems");
+
+                    b.Navigation("ParseLogs");
+                });
+
+            modelBuilder.Entity("MoneyMap.Models.Transaction", b =>
+                {
+                    b.Navigation("Receipts");
+                });
+#pragma warning restore 612, 618
+        }
+    }
+}

MoneyMap/Migrations/20251010025545_LinkCardsToAccounts.cs

@@ -0,0 +1,60 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace MoneyMap.Migrations
+{
+    /// <inheritdoc />
+    public partial class LinkCardsToAccounts : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AddColumn<int>(
+                name: "AccountId",
+                table: "Cards",
+                type: "int",
+                nullable: true);
+
+            migrationBuilder.AddColumn<string>(
+                name: "Nickname",
+                table: "Cards",
+                type: "nvarchar(50)",
+                maxLength: 50,
+                nullable: true);
+
+            migrationBuilder.CreateIndex(
+                name: "IX_Cards_AccountId",
+                table: "Cards",
+                column: "AccountId");
+
+            migrationBuilder.AddForeignKey(
+                name: "FK_Cards_Accounts_AccountId",
+                table: "Cards",
+                column: "AccountId",
+                principalTable: "Accounts",
+                principalColumn: "Id",
+                onDelete: ReferentialAction.Restrict);
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropForeignKey(
+                name: "FK_Cards_Accounts_AccountId",
+                table: "Cards");
+
+            migrationBuilder.DropIndex(
+                name: "IX_Cards_AccountId",
+                table: "Cards");
+
+            migrationBuilder.DropColumn(
+                name: "AccountId",
+                table: "Cards");
+
+            migrationBuilder.DropColumn(
+                name: "Nickname",
+                table: "Cards");
+        }
+    }
+}

MoneyMap/Migrations/MoneyMapContextModelSnapshot.cs

@@ -67,6 +67,9 @@ namespace MoneyMap.Migrations
 
                     SqlServerPropertyBuilderExtensions.UseIdentityColumn(b.Property<int>("Id"));
 
+                    b.Property<int?>("AccountId")
+                        .HasColumnType("int");
+
                     b.Property<string>("Issuer")
                         .IsRequired()
                         .HasMaxLength(100)
@@ -77,6 +80,10 @@ namespace MoneyMap.Migrations
                         .HasMaxLength(4)
                         .HasColumnType("nvarchar(4)");
 
+                    b.Property<string>("Nickname")
+                        .HasMaxLength(50)
+                        .HasColumnType("nvarchar(50)");
+
                     b.Property<string>("Owner")
                         .IsRequired()
                         .HasMaxLength(100)
@@ -84,6 +91,8 @@ namespace MoneyMap.Migrations
 
                     b.HasKey("Id");
 
+                    b.HasIndex("AccountId");
+
                     b.HasIndex("Issuer", "Last4", "Owner");
 
                     b.ToTable("Cards");
@@ -399,6 +408,16 @@ namespace MoneyMap.Migrations
                     b.ToTable("CategoryMappings");
                 });
 
+            modelBuilder.Entity("MoneyMap.Models.Card", b =>
+                {
+                    b.HasOne("MoneyMap.Models.Account", "Account")
+                        .WithMany("Cards")
+                        .HasForeignKey("AccountId")
+                        .OnDelete(DeleteBehavior.Restrict);
+
+                    b.Navigation("Account");
+                });
+
             modelBuilder.Entity("MoneyMap.Models.Receipt", b =>
                 {
                     b.HasOne("MoneyMap.Models.Transaction", "Transaction")
@@ -475,6 +494,8 @@ namespace MoneyMap.Migrations
 
             modelBuilder.Entity("MoneyMap.Models.Account", b =>
                 {
+                    b.Navigation("Cards");
+
                     b.Navigation("DestinationTransfers");
 
                     b.Navigation("SourceTransfers");

MoneyMap/Models/Account.cs

@@ -1,4 +1,5 @@
 using System.ComponentModel.DataAnnotations;
+using System.ComponentModel.DataAnnotations.Schema;
 
 namespace MoneyMap.Models;
 
@@ -32,7 +33,13 @@ public class Account
     public string? Nickname { get; set; } // Optional friendly name like "Emergency Fund"
 
     // Navigation properties
+    public ICollection<Card> Cards { get; set; } = new List<Card>(); // Cards linked to this account
     public ICollection<Transaction> Transactions { get; set; } = new List<Transaction>();
     public ICollection<Transfer> SourceTransfers { get; set; } = new List<Transfer>();
     public ICollection<Transfer> DestinationTransfers { get; set; } = new List<Transfer>();
+
+    [NotMapped]
+    public string DisplayLabel => string.IsNullOrEmpty(Nickname)
+        ? $"{Institution} {Last4} ({AccountType})"
+        : $"{Nickname} ({Institution} {Last4})";
 }

MoneyMap/Models/Card.cs

@@ -1,4 +1,5 @@
 using System.ComponentModel.DataAnnotations;
+using System.ComponentModel.DataAnnotations.Schema;
 using System.Transactions;
 
 namespace MoneyMap.Models;
@@ -8,14 +9,30 @@ public class Card
     [Key]
     public int Id { get; set; }
 
+    [Required]
     [MaxLength(100)]
-    public string Issuer { get; set; } = string.Empty;   // e.g., VISA, MC
+    public string Issuer { get; set; } = string.Empty;   // e.g., VISA, MC, Discover
 
+    [Required]
     [MaxLength(4)]
     public string Last4 { get; set; } = string.Empty;    // "1234"
 
+    [Required]
     [MaxLength(100)]
-    public string Owner { get; set; } = string.Empty;    // optional
+    public string Owner { get; set; } = string.Empty;
+
+    // Link to the account this card draws from/pays to
+    [ForeignKey(nameof(Account))]
+    public int? AccountId { get; set; }
+    public Account? Account { get; set; }
+
+    [MaxLength(50)]
+    public string? Nickname { get; set; } // Optional friendly name
 
     public ICollection<Transaction> Transactions { get; set; } = new List<Transaction>();
+
+    [NotMapped]
+    public string DisplayLabel => string.IsNullOrEmpty(Nickname)
+        ? $"{Issuer} {Last4}"
+        : $"{Nickname} ({Issuer} {Last4})";
 }