feat: add performance logging middleware and enhance performance tracking across services

- Introduced RequestPerfMiddleware to log request performance metrics, including slow request thresholds.
- Updated various services and retrievers to utilize the new performance logging utility for better tracking of execution times.
- Enhanced existing methods with detailed performance logs for operations such as embedding, searching, and indexing.
- Removed deprecated logging setup in stream_new_chat and replaced it with the new performance logger.

surfsense_backend/app/agents/new_chat/chat_deepagent.py

@@ -28,8 +28,9 @@ from app.agents.new_chat.system_prompt import (
 from app.agents.new_chat.tools.registry import build_tools_async
 from app.db import ChatVisibility
 from app.services.connector_service import ConnectorService
+from app.utils.perf import get_perf_logger
 
-_perf_log = logging.getLogger("surfsense.perf")
+_perf_log = get_perf_logger()
 
 # =============================================================================
 # Connector Type Mapping