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.

backend/igny8_core/auth/views.py

@@ -933,12 +933,10 @@ class AuthViewSet(viewsets.GenericViewSet):
                 return success_response(
                     data={
                         'user': user_serializer.data,
-                        'tokens': {
-                            'access': access_token,
-                            'refresh': refresh_token,
-                            'access_expires_at': access_expires_at.isoformat(),
-                            'refresh_expires_at': refresh_expires_at.isoformat(),
-                        }
+                        'access': access_token,
+                        'refresh': refresh_token,
+                        'access_expires_at': access_expires_at.isoformat(),
+                        'refresh_expires_at': refresh_expires_at.isoformat(),
                     },
                     message='Login successful',
                     request=request