party-lock: fix ACL file permissions (0700, owner 1883)

Mosquitto 2.1.2 silently skips ACL file if world-readable or wrong owner.
Listener now sets proper permissions on ACL file writes.
Add CYD lock flash feedback on blocked tap.

infra/party-lock/party-lock.py

@@ -6,6 +6,7 @@
 # ///
 
 import os
+import stat
 
 import paho.mqtt.client as mqtt
 
@@ -22,6 +23,8 @@ def rebuild_acl():
     lines.append("topic readwrite #")
     with open(ACL_PATH, "w") as f:
         f.write("\n".join(lines) + "\n")
+    os.chmod(ACL_PATH, stat.S_IRWXU)
+    os.chown(ACL_PATH, 1883, 1883)
     os.system("docker kill -s HUP mosquitto 2>/dev/null || true")
 
 def on_message(client, userdata, msg):