feat(safety): enhance rate limiting and cost control with alert deduplication and usage tracking

- Added `record_action` in `RateLimiter` for precise tracking of slot consumption post-validation.
- Introduced deduplication mechanism for warning alerts in `CostController` to prevent spamming.
- Refactored `CostController`'s session and daily budget alert handling for improved clarity.
- Implemented test suites for `CostController` and `SafetyGuardian` to validate changes.
- Expanded integration testing to cover deduplication, validation, and loop detection edge cases.

backend/app/services/mcp/client_manager.py

@@ -411,7 +411,20 @@ async def shutdown_mcp_client() -> None:
             _manager_instance = None
 
 
-def reset_mcp_client() -> None:
-    """Reset the global MCP client manager (for testing)."""
+async def reset_mcp_client() -> None:
+    """
+    Reset the global MCP client manager (for testing).
+
+    This is an async function to properly acquire the manager lock
+    and avoid race conditions with get_mcp_client().
+    """
     global _manager_instance
-    _manager_instance = None
+
+    async with _manager_lock:
+        if _manager_instance is not None:
+            # Shutdown gracefully before resetting
+            try:
+                await _manager_instance.shutdown()
+            except Exception:  # noqa: S110
+                pass  # Ignore errors during test cleanup
+        _manager_instance = None