feat: implement long-term user login with refresh tokens

- Introduced a dual-token system for user authentication: a short-lived access token and a long-lived rotating refresh token.
- Created a new RefreshToken model to manage refresh tokens securely.
- Updated auth_api.py to handle login, refresh, and logout processes with the new token system.
- Enhanced security measures including token rotation and theft detection.
- Updated frontend to handle token refresh on 401 errors and adjusted SSE authentication.
- Removed CORS middleware as it's unnecessary behind the nginx proxy.
- Added tests to ensure functionality and security of the new token system.

backend/api/error_codes.py

@@ -12,6 +12,9 @@ INVALID_CREDENTIALS = "INVALID_CREDENTIALS"
 NOT_VERIFIED = "NOT_VERIFIED"
 ACCOUNT_MARKED_FOR_DELETION = "ACCOUNT_MARKED_FOR_DELETION"
 ALREADY_MARKED = "ALREADY_MARKED"
+REFRESH_TOKEN_REUSE = "REFRESH_TOKEN_REUSE"
+REFRESH_TOKEN_EXPIRED = "REFRESH_TOKEN_EXPIRED"
+MISSING_REFRESH_TOKEN = "MISSING_REFRESH_TOKEN"
 
 
 class ErrorCodes: