Add double Ctrl+C handling to wssshd for force exit

- Implement double SIGINT (Ctrl+C) detection in wssshd server
- First Ctrl+C: Initiates graceful shutdown with cleanup
- Second Ctrl+C: Forces immediate exit using os._exit(1) without cleanup
- Consistent behavior with wssshc double Ctrl+C handling
- Prevents hanging during shutdown when graceful shutdown fails
- Maintains backward compatibility with single Ctrl+C graceful shutdown

This ensures wssshd can be forcefully terminated if graceful shutdown gets stuck, while still allowing proper cleanup on normal shutdown.

wsssd/server.py

@@ -195,10 +195,19 @@ async def run_server():
 
     # Set up signal handling for clean exit
     shutdown_event.clear()
+    sigint_count = 0
 
     def signal_handler(signum, frame):
-        if debug: print(f"[DEBUG] Received signal {signum}, initiating shutdown")
-        shutdown_event.set()
+        nonlocal sigint_count
+        sigint_count += 1
+
+        if sigint_count == 1:
+            print("\nReceived SIGINT, attempting graceful shutdown...")
+            shutdown_event.set()
+        elif sigint_count >= 2:
+            print("\nReceived second SIGINT, exiting immediately...")
+            # Force exit without cleanup
+            os._exit(1)
 
     # Register signal handler for SIGINT (Ctrl+C)
     signal.signal(signal.SIGINT, signal_handler)