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/planning/PlanningService.java

@@ -0,0 +1,29 @@
+package com.recipeapp.planning;
+
+import com.recipeapp.planning.dto.*;
+import java.time.LocalDate;
+import java.util.List;
+import java.util.UUID;
+
+public interface PlanningService {
+
+    WeekPlanResponse getWeekPlan(UUID householdId, LocalDate weekStart);
+
+    WeekPlanResponse createWeekPlan(UUID householdId, LocalDate weekStart);
+
+    SlotResponse addSlot(UUID householdId, UUID planId, CreateSlotRequest request);
+
+    SlotResponse updateSlot(UUID householdId, UUID planId, UUID slotId, UpdateSlotRequest request);
+
+    void deleteSlot(UUID householdId, UUID planId, UUID slotId);
+
+    WeekPlanResponse confirmPlan(UUID householdId, UUID planId);
+
+    SuggestionResponse getSuggestions(UUID householdId, UUID planId, LocalDate slotDate);
+
+    VarietyScoreResponse getVarietyScore(UUID householdId, UUID planId);
+
+    CookingLogResponse createCookingLog(UUID householdId, UUID userId, CreateCookingLogRequest request);
+
+    List<CookingLogResponse> listCookingLogs(UUID householdId, int limit, int offset);
+}