feat(auth): add @RequiresHouseholdRole annotation with interceptor

Reusable annotation for planner-only endpoints. Uses a
HandlerInterceptor that resolves the household role from the
authenticated user and throws 403 if the role doesn't match.

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

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

@@ -24,6 +24,10 @@ public class HouseholdResolver {
         return findMembership(userEmail).getUser().getId();
     }
 
+    public String resolveRole(String userEmail) {
+        return findMembership(userEmail).getRole();
+    }
+
     private HouseholdMember findMembership(String userEmail) {
         return householdMemberRepository.findByUserEmailIgnoreCase(userEmail)
                 .orElseThrow(() -> new ResourceNotFoundException("User is not in a household"));