Error Handling: Standardize error handling and responses

[OneByJorah]

Error Handling Gap

Current State: Basic try/except with generic 500 errors. No standardized error response format, no error codes, no client-friendly error messages.

Required:

1. Standardized Error Response Format:

2. Custom Exception Classes:

   • ValidationError (400)
   • AuthenticationError (401)
   • AuthorizationError (403)
   • NotFoundError (404)
   • ConflictError (409)
   • RateLimitError (429)
   • InternalError (500)
   • ServiceUnavailableError (503)

3. Global Error Handler:

   • Catch all exceptions
   • Log with full stack trace
   • Return standardized response
   • Include request ID for tracing

4. Frontend Error Handling:

   • Global error boundary
   • API error interceptor
   • User-friendly error toasts
   • Retry logic for transient errors

5. Frontend:

   • Add error boundary component
   • Add axios interceptor for 401/403/5xx handling
   • Add retry logic for transient failures

Priority: HIGH