🛡️ Add rate limiting to API calls in the frontend

[jobbykings]

Summary

The frontend makes unbounded API calls in some scenarios (e.g., rapid user interactions), which can overload the backend.

Tasks

• Implement debouncing for search inputs
• Add request deduplication for concurrent identical requests
• Implement client-side rate limiting for mutation operations
• Add retry with backoff for failed requests

Acceptance Criteria

• Search inputs debounced by 300ms
• Duplicate concurrent requests are deduplicated