feat: Add stock transaction tracking system

- Add StockTransaction entity for audit trail
- Track received, used, adjusted, scrapped, and returned stock
- Include unit price tracking for cost analysis
- Link transactions to jobs and suppliers

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

CutList.Web/Migrations/20260204221152_AddPriceTrackingToTransactions.cs

@@ -0,0 +1,61 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace CutList.Web.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddPriceTrackingToTransactions : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AddColumn<int>(
+                name: "SupplierId",
+                table: "StockTransactions",
+                type: "int",
+                nullable: true);
+
+            migrationBuilder.AddColumn<decimal>(
+                name: "UnitPrice",
+                table: "StockTransactions",
+                type: "decimal(10,2)",
+                precision: 10,
+                scale: 2,
+                nullable: true);
+
+            migrationBuilder.CreateIndex(
+                name: "IX_StockTransactions_SupplierId",
+                table: "StockTransactions",
+                column: "SupplierId");
+
+            migrationBuilder.AddForeignKey(
+                name: "FK_StockTransactions_Suppliers_SupplierId",
+                table: "StockTransactions",
+                column: "SupplierId",
+                principalTable: "Suppliers",
+                principalColumn: "Id",
+                onDelete: ReferentialAction.SetNull);
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropForeignKey(
+                name: "FK_StockTransactions_Suppliers_SupplierId",
+                table: "StockTransactions");
+
+            migrationBuilder.DropIndex(
+                name: "IX_StockTransactions_SupplierId",
+                table: "StockTransactions");
+
+            migrationBuilder.DropColumn(
+                name: "SupplierId",
+                table: "StockTransactions");
+
+            migrationBuilder.DropColumn(
+                name: "UnitPrice",
+                table: "StockTransactions");
+        }
+    }
+}