Implement Gunicorn+Uvicorn integration for shared data preloading

- Create run_with_gunicorn.py script to properly initialize shared data in the
  main process before forking worker processes
- Revert unvicorn to single process mode only, and let gunicorn do all the multi-process jobs

gunicorn_config.py

@@ -0,0 +1,80 @@
+# gunicorn_config.py
+import os
+import multiprocessing
+from lightrag.kg.shared_storage import finalize_share_data
+from lightrag.api.utils_api import parse_args
+
+# Parse command line arguments
+args = parse_args()
+
+# Determine worker count - from environment variable or command line arguments
+workers = int(os.getenv('WORKERS', args.workers))
+
+# If not specified, use CPU count * 2 + 1 (Gunicorn recommended configuration)
+if workers <= 1:
+    workers = multiprocessing.cpu_count() * 2 + 1
+
+# Binding address
+bind = f"{os.getenv('HOST', args.host)}:{os.getenv('PORT', args.port)}"
+
+# Enable preload_app option
+preload_app = True
+
+# Use Uvicorn worker
+worker_class = "uvicorn.workers.UvicornWorker"
+
+# Other Gunicorn configurations
+timeout = int(os.getenv('TIMEOUT', 120))
+keepalive = 5
+
+# Optional SSL configuration
+if args.ssl:
+    certfile = args.ssl_certfile
+    keyfile = args.ssl_keyfile
+
+# Logging configuration
+errorlog = os.getenv('ERROR_LOG', '-')  # '-' means stderr
+accesslog = os.getenv('ACCESS_LOG', '-')  # '-' means stderr
+loglevel = os.getenv('LOG_LEVEL', 'info')
+
+def on_starting(server):
+    """
+    Executed when Gunicorn starts, before forking the first worker processes
+    You can use this function to do more initialization tasks for all processes
+    """
+    print("=" * 80)
+    print(f"GUNICORN MASTER PROCESS: on_starting jobs for all {workers} workers")
+    print(f"Process ID: {os.getpid()}")
+    print("=" * 80)
+    
+    # Memory usage monitoring
+    try:
+        import psutil
+        process = psutil.Process(os.getpid())
+        memory_info = process.memory_info()
+        msg = f"Memory usage after initialization: {memory_info.rss / 1024 / 1024:.2f} MB"
+        print(msg)
+    except ImportError:
+        print("psutil not installed, skipping memory usage reporting")
+    
+    print("=" * 80)
+    print("Gunicorn initialization complete, forking workers...")
+    print("=" * 80)
+
+
+def on_exit(server):
+    """
+    Executed when Gunicorn is shutting down.
+    This is a good place to release shared resources.
+    """
+    print("=" * 80)
+    print("GUNICORN MASTER PROCESS: Shutting down")
+    print(f"Process ID: {os.getpid()}")
+    print("=" * 80)
+    
+    # Release shared resources
+    finalize_share_data()
+    
+    print("=" * 80)
+    print("Gunicorn shutdown complete")
+    print("=" * 80)