fix: make Ctrl-C work on Windows by setting accept() timeout

socket.accept() on Windows blocks indefinitely and ignores KeyboardInterrupt.
Setting a 1-second timeout on the server socket causes the accept loop to wake
up every second and re-check, so Ctrl-C is handled within ~1 second.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

bridges/ach_server.py

@@ -376,6 +376,9 @@ def serve(args: argparse.Namespace) -> None:
     server_sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
     server_sock.bind(("0.0.0.0", args.port))
     server_sock.listen(5)
+    # Wake up every second so Ctrl-C is handled promptly on Windows.
+    # Without this, accept() blocks indefinitely and ignores KeyboardInterrupt.
+    server_sock.settimeout(1.0)
 
     max_ev = args.max_events
     print(f"\n{'='*60}")
@@ -399,6 +402,9 @@ def serve(args: argparse.Namespace) -> None:
         while True:
             try:
                 client_sock, addr = server_sock.accept()
+            except socket.timeout:
+                continue  # no connection this second; loop back and check for Ctrl-C
+            try:
                 peer_ip = addr[0]
                 peer = f"{addr[0]}:{addr[1]}"