feat: WeChat Linux bot via docker-wechatbot-webhook

- Docker container with auto-restart
- systemd webhook receiver on :5804
- Full send/receive loop: WeChat ↔ Docker ↔ Hermes
- Fixed login token for persistence
- Firewall rules for container-host communication

gateway/linux/wechat-webhook.service

@@ -0,0 +1,23 @@
+[Unit]
+Description=WeChat Webhook Receiver — bridges WeChat bot messages to Hermes
+After=network-online.target docker.service
+Wants=network-online.target
+BindsTo=docker.service
+
+[Service]
+Type=simple
+User=hmo
+WorkingDirectory=/home/hmo/projects/AgentsMeeting/gateway/linux
+ExecStart=/usr/bin/python3 /home/hmo/projects/AgentsMeeting/gateway/linux/wechat_webhook.py
+Restart=always
+RestartSec=5
+StandardOutput=append:/home/hmo/projects/AgentsMeeting/gateway/linux/logs/webhook_service.log
+StandardError=append:/home/hmo/projects/AgentsMeeting/gateway/linux/logs/webhook_service.log
+
+# Don't inherit system proxy (Hermes is local)
+Environment=no_proxy=192.168.1.246,localhost,127.0.0.1,172.17.0.0/16
+Environment=http_proxy=
+Environment=https_proxy=
+
+[Install]
+WantedBy=multi-user.target