feat(shopping): add generated_at column to shopping_list

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

backend/src/main/java/com/recipeapp/shopping/entity/ShoppingList.java

@@ -3,6 +3,7 @@ package com.recipeapp.shopping.entity;
 import com.recipeapp.household.entity.Household;
 import com.recipeapp.planning.entity.WeekPlan;
 import jakarta.persistence.*;
+import java.time.Instant;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.UUID;
@@ -23,6 +24,9 @@ public class ShoppingList {
     @JoinColumn(name = "week_plan_id", nullable = false)
     private WeekPlan weekPlan;
 
+    @Column(name = "generated_at", nullable = false)
+    private Instant generatedAt = Instant.now();
+
     @OneToMany(mappedBy = "shoppingList", cascade = CascadeType.ALL, orphanRemoval = true)
     private List<ShoppingListItem> items = new ArrayList<>();
 
@@ -36,5 +40,7 @@ public class ShoppingList {
     public UUID getId() { return id; }
     public Household getHousehold() { return household; }
     public WeekPlan getWeekPlan() { return weekPlan; }
+    public Instant getGeneratedAt() { return generatedAt; }
+    public void setGeneratedAt(Instant generatedAt) { this.generatedAt = generatedAt; }
     public List<ShoppingListItem> getItems() { return items; }
 }

backend/src/main/resources/db/migration/V022__add_shopping_list_generated_at.sql

@@ -0,0 +1,2 @@
+ALTER TABLE shopping_list
+    ADD COLUMN generated_at timestamptz NOT NULL DEFAULT now();