Add refresh token functionality and improve login response handling

- Introduced RefreshTokenView to allow users to refresh their access tokens using a valid refresh token.
- Enhanced LoginView to ensure correct user/account loading and improved error handling during user serialization.
- Updated API response structure to include access and refresh token expiration times.
- Adjusted frontend API handling to support both new and legacy token response formats.

docs/API-COMPLETE-REFERENCE.md

@@ -644,9 +644,12 @@ class KeywordViewSet(SiteSectorModelViewSet):
   "data": {
     "user": { ... },
     "access": "eyJ0eXAiOiJKV1QiLCJhbGc...",
-    "refresh": "eyJ0eXAiOiJKV1QiLCJhbGc..."
+    "refresh": "eyJ0eXAiOiJKV1QiLCJhbGc...",
+    "access_expires_at": "2025-01-XXT...",
+    "refresh_expires_at": "2025-01-XXT..."
   },
-  "message": "Login successful"
+  "message": "Login successful",
+  "request_id": "550e8400-e29b-41d4-a716-446655440000"
 }
 ```