Fix double Ctrl+C signal handling in wssshd

- Replaced counter-based signal handling with flag-based approach
- Added sigint_handled flag to prevent multiple signal handler executions
- First Ctrl+C: Sets flag and initiates graceful shutdown
- Second Ctrl+C: Forces immediate exit with os._exit(1)
- Prevents race conditions and multiple signal handler calls
- Ensures proper single-signal behavior for graceful shutdown

This resolves the issue where a single Ctrl+C was triggering both graceful shutdown and immediate exit messages.

wsssd/server.py

@@ -237,20 +237,19 @@ async def run_server():
 
     # Set up signal handling for clean exit
     shutdown_event.clear()
-    sigint_count = 0
+    sigint_handled = False
 
     def signal_handler(signum, frame):
-        nonlocal sigint_count
-        sigint_count += 1
-
-        if sigint_count == 1:
-            print("\nReceived SIGINT, attempting graceful shutdown...")
-            shutdown_event.set()
-        elif sigint_count >= 2:
+        nonlocal sigint_handled
+        if sigint_handled:
+            # Already handling a signal, force exit
             print("\nReceived second SIGINT, exiting immediately...")
-            # Force exit without cleanup
             os._exit(1)
 
+        sigint_handled = True
+        print("\nReceived SIGINT, attempting graceful shutdown...")
+        shutdown_event.set()
+
     # Register signal handler for SIGINT (Ctrl+C)
     signal.signal(signal.SIGINT, signal_handler)