feat: drop QuantityOnHand column and StockTransactions table

Final step of removing inventory quantity tracking - see
docs/superpowers/specs/2026-08-01-remove-inventory-quantity-tracking-design.md.
Destructive to any existing on-hand/transaction data; confirmed
acceptable since nothing read it automatically.

CutList.Web/Data/ApplicationDbContext.cs

@@ -13,7 +13,6 @@ public class ApplicationDbContext : DbContext
     public DbSet<Material> Materials => Set<Material>();
     public DbSet<MaterialDimensions> MaterialDimensions => Set<MaterialDimensions>();
     public DbSet<StockItem> StockItems => Set<StockItem>();
-    public DbSet<StockTransaction> StockTransactions => Set<StockTransaction>();
     public DbSet<CuttingTool> CuttingTools => Set<CuttingTool>();
     public DbSet<Job> Jobs => Set<Job>();
     public DbSet<JobPart> JobParts => Set<JobPart>();
@@ -157,24 +156,6 @@ public class ApplicationDbContext : DbContext
             entity.HasIndex(e => new { e.MaterialId, e.LengthInches }).IsUnique();
         });
 
-        // StockTransaction
-        modelBuilder.Entity<StockTransaction>(entity =>
-        {
-            entity.HasKey(e => e.Id);
-            entity.Property(e => e.Notes).HasMaxLength(500);
-            entity.Property(e => e.CreatedAt).HasDefaultValueSql("GETUTCDATE()");
-
-            entity.HasOne(e => e.StockItem)
-                .WithMany(s => s.Transactions)
-                .HasForeignKey(e => e.StockItemId)
-                .OnDelete(DeleteBehavior.Cascade);
-
-            entity.HasOne(e => e.Job)
-                .WithMany()
-                .HasForeignKey(e => e.JobId)
-                .OnDelete(DeleteBehavior.SetNull);
-        });
-
         // CuttingTool
         modelBuilder.Entity<CuttingTool>(entity =>
         {

CutList.Web/Data/Entities/StockItem.cs

@@ -6,12 +6,10 @@ public class StockItem
     public int MaterialId { get; set; }
     public decimal LengthInches { get; set; }
     public string? Name { get; set; }
-    public int QuantityOnHand { get; set; } = 0;
     public string? Notes { get; set; }
     public bool IsActive { get; set; } = true;
     public DateTime CreatedAt { get; set; } = DateTime.UtcNow;
     public DateTime? UpdatedAt { get; set; }
 
     public Material Material { get; set; } = null!;
-    public ICollection<StockTransaction> Transactions { get; set; } = new List<StockTransaction>();
 }

CutList.Web/Data/Entities/StockTransaction.cs

@@ -1,24 +0,0 @@
-namespace CutList.Web.Data.Entities;
-
-public class StockTransaction
-{
-    public int Id { get; set; }
-    public int StockItemId { get; set; }
-    public int Quantity { get; set; }
-    public StockTransactionType Type { get; set; }
-    public int? JobId { get; set; }
-    public string? Notes { get; set; }
-    public DateTime CreatedAt { get; set; } = DateTime.UtcNow;
-
-    public StockItem StockItem { get; set; } = null!;
-    public Job? Job { get; set; }
-}
-
-public enum StockTransactionType
-{
-    Received,
-    Used,
-    Adjustment,
-    Scrapped,
-    Returned
-}