Enhance signal handling and suppress warnings in simulation scripts

- Added signal handling to gracefully manage shutdown events across simulation scripts, ensuring proper cleanup of resources.
- Introduced a global shutdown event to allow simulations to respond to termination signals, improving robustness.
- Suppressed warnings related to multiprocessing resource tracking to avoid unnecessary log clutter during execution.
- Updated cleanup logic in `SimulationRunner` and `ZepGraphMemoryManager` to prevent redundant calls and ensure efficient resource management.
- Enhanced logging to provide clearer feedback during shutdown processes, improving traceability.

backend/app/__init__.py

@@ -3,6 +3,12 @@ MiroFish Backend - Flask应用工厂
 """
 
 import os
+import warnings
+
+# 抑制 multiprocessing resource_tracker 的警告（来自第三方库如 transformers）
+# 需要在所有其他导入之前设置
+warnings.filterwarnings("ignore", message=".*resource_tracker.*")
+
 from flask import Flask, request
 from flask_cors import CORS