Implement Recipe, Planning, Shopping, Pantry, and Admin domains

Outside-in TDD for all 5 remaining domains (128 tests total):
- Recipe: CRUD, ingredients autocomplete/patch, tags, categories (27 tests)
- Planning: week plans, slots, confirm, suggestions, variety score, cooking logs (24 tests)
- Shopping: generate from plan, publish, check/add/remove items (15 tests)
- Pantry: CRUD with expiry sorting (11 tests)
- Admin: user management, password reset, audit logging (13 tests)

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

backend/src/main/java/com/recipeapp/recipe/RecipeService.java

@@ -0,0 +1,35 @@
+package com.recipeapp.recipe;
+
+import com.recipeapp.recipe.dto.*;
+import java.util.List;
+import java.util.UUID;
+
+public interface RecipeService {
+
+    List<RecipeSummaryResponse> listRecipes(UUID householdId, String search, String effort,
+                                             Boolean isChildFriendly, Integer cookTimeMaxMin,
+                                             String sort, int limit, int offset);
+
+    long countRecipes(UUID householdId, String search, String effort,
+                      Boolean isChildFriendly, Integer cookTimeMaxMin);
+
+    RecipeDetailResponse getRecipe(UUID householdId, UUID recipeId);
+
+    RecipeDetailResponse createRecipe(UUID householdId, RecipeCreateRequest request);
+
+    RecipeDetailResponse updateRecipe(UUID householdId, UUID recipeId, RecipeCreateRequest request);
+
+    void deleteRecipe(UUID householdId, UUID recipeId);
+
+    List<IngredientResponse> searchIngredients(UUID householdId, String search, Boolean isStaple);
+
+    IngredientResponse patchIngredient(UUID householdId, UUID ingredientId, IngredientPatchRequest request);
+
+    List<TagResponse> listTags(UUID householdId);
+
+    TagResponse createTag(UUID householdId, TagCreateRequest request);
+
+    List<IngredientCategoryResponse> listCategories(UUID householdId);
+
+    IngredientCategoryResponse createCategory(UUID householdId, IngredientCategoryCreateRequest request);
+}