feat: exec channel auto-parses JSON stdout into template variables

feat: add Exec channel — map WeChat commands to shell execution

feat: add /? and /cmd? command help discovery in WeChat

feat: full media message support + API hardening

feat: full media message support (receive + CDN download/upload + send)

feat: add IFTTT channel for bidirectional automation

fix: webhook accepts GET+POST for QNAP SMS provider compatibility

feat: webhook supports query params, add QNAP SMS provider example

docs: replace doorbell with ha endpoint, add HA notify integration guide

feat: store credentials in ~/.wechat-gateway/ instead of data/

feat: support /etc/wechat-gateway/config.yaml, auto-generate on setup

feat: add npm run setup-service for one-command systemd registration

docs: expand deployment guide with step-by-step instructions

docs: add detailed channel usage guide with examples

init: wechat-gateway with Gateway + Channel plugin architecture