feat: Add optimization result persistence to Job entity

Add OptimizationResultJson and OptimizedAt columns to Job table.
JobService now saves/clears optimization results and auto-clears
stale results when parts, stock, or cutting tool change.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

CutList.Web/Migrations/ApplicationDbContextModelSnapshot.cs

@@ -119,6 +119,12 @@ namespace CutList.Web.Migrations
                     b.Property<string>("Notes")
                         .HasColumnType("nvarchar(max)");
 
+                    b.Property<string>("OptimizationResultJson")
+                        .HasColumnType("nvarchar(max)");
+
+                    b.Property<DateTime?>("OptimizedAt")
+                        .HasColumnType("datetime2");
+
                     b.Property<DateTime?>("UpdatedAt")
                         .HasColumnType("datetime2");