feat(shopping): add GET /v1/shopping-lists endpoint and planner-only guard

New week-based lookup endpoint with optional weekStart param (defaults
to current week). Generate endpoint now enforced with @RequiresHouseholdRole.

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

backend/src/main/java/com/recipeapp/shopping/ShoppingListController.java

@@ -1,11 +1,14 @@
 package com.recipeapp.shopping;
 
+import com.recipeapp.common.RequiresHouseholdRole;
+import com.recipeapp.common.ResourceNotFoundException;
 import com.recipeapp.recipe.HouseholdResolver;
 import com.recipeapp.shopping.dto.*;
 import org.springframework.http.HttpStatus;
 import org.springframework.web.bind.annotation.*;
 
 import java.security.Principal;
+import java.time.LocalDate;
 import java.util.UUID;
 
 @RestController
@@ -19,8 +22,21 @@ public class ShoppingListController {
         this.householdResolver = householdResolver;
     }
 
+    @GetMapping("/v1/shopping-lists")
+    public ShoppingListResponse getByWeekStart(
+            @RequestParam(required = false) LocalDate weekStart,
+            Principal principal) {
+        UUID householdId = householdResolver.resolve(principal.getName());
+        ShoppingListResponse response = shoppingService.getByWeekStart(householdId, weekStart);
+        if (response == null) {
+            throw new ResourceNotFoundException("No shopping list for this week");
+        }
+        return response;
+    }
+
     @PostMapping("/v1/week-plans/{id}/shopping-list")
     @ResponseStatus(HttpStatus.CREATED)
+    @RequiresHouseholdRole("planner")
     public ShoppingListResponse generateFromPlan(@PathVariable UUID id, Principal principal) {
         UUID householdId = householdResolver.resolve(principal.getName());
         return shoppingService.generateFromPlan(householdId, id);