feat: add 7 new features — exec shell, SSE events, compose import, docker resources, resource limits, email notifications, auto-updates

- Container exec/shell via WebSocket + xterm.js (subtle >_ button on cards)
- Live dashboard updates via SSE (resource alerts, health changes, update notices)
- Docker Compose import with YAML parsing, preview, and dependency-ordered deploy
- Volume & network management modal with disk usage overview
- CPU/memory resource limits on deploy and live update
- Email SMTP notifications (nodemailer) alongside Discord/Telegram/ntfy
- Scheduled auto-update scheduler with maintenance windows (daily/weekly/monthly)

New deps: ws, js-yaml, nodemailer

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

dashcaddy-api/routes/apps/index.js

@@ -4,6 +4,7 @@ const initDeploy = require('./deploy');
 const initRemoval = require('./removal');
 const initTemplates = require('./templates');
 const initRestore = require('./restore');
+const initCompose = require('./compose');
 
 /**
  * Apps routes aggregator
@@ -44,6 +45,7 @@ module.exports = function(ctx) {
   router.use(initRemoval(subCtx));
   router.use(initTemplates(subCtx));
   router.use(initRestore(subCtx));
+  router.use(initCompose(subCtx));
 
   return router;
 };