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/IngredientController.java

@@ -0,0 +1,41 @@
+package com.recipeapp.recipe;
+
+import com.recipeapp.recipe.dto.*;
+import jakarta.validation.Valid;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.*;
+
+import java.security.Principal;
+import java.util.List;
+import java.util.UUID;
+
+@RestController
+@RequestMapping("/v1/ingredients")
+public class IngredientController {
+
+    private final RecipeService recipeService;
+    private final HouseholdResolver householdResolver;
+
+    public IngredientController(RecipeService recipeService, HouseholdResolver householdResolver) {
+        this.recipeService = recipeService;
+        this.householdResolver = householdResolver;
+    }
+
+    @GetMapping
+    public List<IngredientResponse> searchIngredients(
+            Principal principal,
+            @RequestParam(required = false) String search,
+            @RequestParam(required = false) Boolean isStaple) {
+        UUID householdId = householdResolver.resolve(principal.getName());
+        return recipeService.searchIngredients(householdId, search, isStaple);
+    }
+
+    @PatchMapping("/{id}")
+    public IngredientResponse patchIngredient(
+            Principal principal,
+            @PathVariable UUID id,
+            @Valid @RequestBody IngredientPatchRequest request) {
+        UUID householdId = householdResolver.resolve(principal.getName());
+        return recipeService.patchIngredient(householdId, id, request);
+    }
+}