- Add 'enabled' field to ProxyConfig for preserving config when disabled
- Mask proxy password in API responses (return '***' instead of actual password)
- Preserve existing password on update when new password not provided
- Add URL encoding for proxy credentials (handle special chars like @, :, /)
- Enhanced URL validation: block SOCKS4, require valid host, forbid embedded auth
- UI improvements: use Switch component, dynamic password placeholder
- Add confirmation dialog for orphaned credentials (URL empty but has username/password)
- Prevent browser password autofill with randomized IDs and CSS text-security
- Unify ProxyConfig type definition in types.ts
- Add proxy field to ProviderEndpoint database model with migration
- Add ProxyConfig Pydantic model for proxy URL validation
- Extend HTTP client pool with create_client_with_proxy method
- Integrate proxy configuration in chat_handler_base.py and cli_handler_base.py
- Update admin API endpoints to support proxy configuration CRUD
- Add proxy configuration UI in frontend EndpointFormDialog
Fixes#28
