Add structured quantities + units to shopping list items

Mirrors the Phase 2 work on RecipeIngredient: ShoppingListItem grows
Quantity (decimal), UnitOfMeasureId / FamilyUnitOfMeasureId, IsApproximate,
and QuantityNote. The recipe-to-list copy now carries structured fields
verbatim instead of folding them into the free-form Name, and the
unit-in-use guard now also blocks deleting a family unit that's referenced
by a shopping list item.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/backend/YesChef.Api/Migrations/YesChefDbModelSnapshot.cs

@@ -514,6 +514,12 @@ namespace YesChef.Api.Migrations
                     b.Property<int?>("FamilyProductId")
                         .HasColumnType("integer");
 
+                    b.Property<int?>("FamilyUnitOfMeasureId")
+                        .HasColumnType("integer");
+
+                    b.Property<bool>("IsApproximate")
+                        .HasColumnType("boolean");
+
                     b.Property<bool>("IsChecked")
                         .HasColumnType("boolean");
 
@@ -525,6 +531,14 @@ namespace YesChef.Api.Migrations
                     b.Property<int?>("ProductId")
                         .HasColumnType("integer");
 
+                    b.Property<decimal?>("Quantity")
+                        .HasPrecision(12, 4)
+                        .HasColumnType("numeric(12,4)");
+
+                    b.Property<string>("QuantityNote")
+                        .HasMaxLength(200)
+                        .HasColumnType("character varying(200)");
+
                     b.Property<int?>("RecipeId")
                         .HasColumnType("integer");
 
@@ -543,6 +557,9 @@ namespace YesChef.Api.Migrations
                     b.Property<int>("SortOrder")
                         .HasColumnType("integer");
 
+                    b.Property<int?>("UnitOfMeasureId")
+                        .HasColumnType("integer");
+
                     b.HasKey("Id");
 
                     b.HasIndex("CheckedByUserId");
@@ -551,6 +568,8 @@ namespace YesChef.Api.Migrations
 
                     b.HasIndex("FamilyProductId");
 
+                    b.HasIndex("FamilyUnitOfMeasureId");
+
                     b.HasIndex("ProductId");
 
                     b.HasIndex("RecipeId");
@@ -561,6 +580,8 @@ namespace YesChef.Api.Migrations
 
                     b.HasIndex("ShoppingListId");
 
+                    b.HasIndex("UnitOfMeasureId");
+
                     b.ToTable("ShoppingListItems");
                 });
 
@@ -965,6 +986,11 @@ namespace YesChef.Api.Migrations
                         .HasForeignKey("FamilyProductId")
                         .OnDelete(DeleteBehavior.SetNull);
 
+                    b.HasOne("YesChef.Api.Entities.FamilyUnitOfMeasure", "FamilyUnitOfMeasure")
+                        .WithMany()
+                        .HasForeignKey("FamilyUnitOfMeasureId")
+                        .OnDelete(DeleteBehavior.Restrict);
+
                     b.HasOne("YesChef.Api.Entities.Product", "Product")
                         .WithMany()
                         .HasForeignKey("ProductId")
@@ -991,12 +1017,19 @@ namespace YesChef.Api.Migrations
                         .OnDelete(DeleteBehavior.Cascade)
                         .IsRequired();
 
+                    b.HasOne("YesChef.Api.Entities.UnitOfMeasure", "UnitOfMeasure")
+                        .WithMany()
+                        .HasForeignKey("UnitOfMeasureId")
+                        .OnDelete(DeleteBehavior.Restrict);
+
                     b.Navigation("CheckedByUser");
 
                     b.Navigation("Family");
 
                     b.Navigation("FamilyProduct");
 
+                    b.Navigation("FamilyUnitOfMeasure");
+
                     b.Navigation("Product");
 
                     b.Navigation("Recipe");
@@ -1006,6 +1039,8 @@ namespace YesChef.Api.Migrations
                     b.Navigation("Section");
 
                     b.Navigation("ShoppingList");
+
+                    b.Navigation("UnitOfMeasure");
                 });
 
             modelBuilder.Entity("YesChef.Api.Entities.Store", b =>