feat: enhance caching mechanisms to prevent memory leaks

- Improved in-memory rate limiting by evicting timestamps outside the current window and cleaning up empty keys.
- Updated LLM router service to cache context profiles and avoid redundant computations.
- Introduced cache eviction logic for MCP tools and sandbox instances to manage memory usage effectively.
- Added garbage collection triggers in chat streaming functions to reclaim resources promptly.

surfsense_backend/app/services/llm_service.py

@@ -12,6 +12,7 @@ from app.services.llm_router_service import (
     AUTO_MODE_ID,
     ChatLiteLLMRouter,
     LLMRouterService,
+    get_auto_mode_llm,
     is_auto_mode,
 )
 
@@ -221,7 +222,7 @@ async def get_search_space_llm_instance(
                 logger.debug(
                     f"Using Auto mode (LLM Router) for search space {search_space_id}, role {role}"
                 )
-                return ChatLiteLLMRouter(disable_streaming=disable_streaming)
+                return get_auto_mode_llm(streaming=not disable_streaming)
             except Exception as e:
                 logger.error(f"Failed to create ChatLiteLLMRouter: {e}")
                 return None