Add test infrastructure and example vault content

- Add docker-compose.test.yml for isolated testing
- Add test vault with sample Markdown notes across categories
- Add frontend audit script for module validation
- Increment user failed_attempts in test data

data/users.json

@@ -13,7 +13,7 @@
       "active": true,
       "created_at": "2026-03-23T19:38:00.742597+00:00",
       "last_login": null,
-      "failed_attempts": 0,
+      "failed_attempts": 2,
       "locked_until": null
     }
   }