fix(security): use generic forbidden message to avoid leaking required role

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

backend/src/test/java/com/recipeapp/common/HouseholdRoleInterceptorTest.java

@@ -62,7 +62,7 @@ class HouseholdRoleInterceptorTest {
 
         assertThatThrownBy(() -> interceptor.preHandle(request, response, handlerMethod))
                 .isInstanceOf(ForbiddenException.class)
-                .hasMessageContaining("planner");
+                .hasMessage("Insufficient permissions");
     }
 
     @Test