fix: Resolve import errors in database connector

- Remove unused PBKDF2 import that was causing ImportError
- Add missing Tuple import in database_config_ui.py
- All basic functionality tests now pass successfully

The database connector is now ready for integration with:
- MySQL/MariaDB support
- PostgreSQL support
- Connection pooling
- Credential encryption
- Query caching
- Rate limiting
- UI configuration schema
- Comprehensive error handling

common/data_source/database_config_ui.py

@@ -21,7 +21,7 @@ Provides UI schema and validation for database connector configuration.
 This integrates with RAGFlow's data source configuration UI.
 """
 
-from typing import Dict, List, Any, Optional
+from typing import Dict, List, Any, Optional, Tuple
 from enum import Enum
 
 

common/data_source/database_connector.py

@@ -49,8 +49,6 @@ from queue import Queue, Empty
 from contextlib import contextmanager
 import base64
 from cryptography.fernet import Fernet
-from cryptography.hazmat.primitives import hashes
-from cryptography.hazmat.primitives.kdf.pbkdf2 import PBKDF2
 from collections import defaultdict, deque
 
 from common.data_source.interfaces import LoadConnector, PollConnector, CredentialsConnector