security: Implemented API key redaction for secure logging

- Add redact_key_for_logging() helper function to show only first/last 6 chars
- Fix API key exposure in app/service/key/key_manager.py line 68
- Apply key redaction across all Python files with API key logging
- Standardize logging security across 17 files including routers, services, handlers

app/database/services.py

@@ -8,6 +8,7 @@ import json
 from app.database.connection import database
 from app.database.models import Settings, ErrorLog, RequestLog, FileRecord, FileState
 from app.log.logger import get_database_logger
+from app.utils.helpers import redact_key_for_logging
 
 logger = get_database_logger()
 
@@ -143,7 +144,7 @@ async def add_error_log(
             )
         )
         await database.execute(query)
-        logger.info(f"Added error log for key: {gemini_key}")
+        logger.info(f"Added error log for key: {redact_key_for_logging(gemini_key)}")
         return True
     except Exception as e:
         logger.error(f"Failed to add error log: {str(e)}")