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/deploy.js

@@ -170,6 +170,18 @@ module.exports = function({ docker, caddy, credentialManager, servicesStateManag
         containerConfig.HostConfig.CapAdd = processedTemplate.docker.capabilities;
       }
 
+      // Resource limits (CPU and memory)
+      if (userConfig.resources) {
+        if (userConfig.resources.memory) {
+          const memBytes = Math.round(userConfig.resources.memory * 1024 * 1024); // MB to bytes
+          containerConfig.HostConfig.Memory = memBytes;
+          containerConfig.HostConfig.MemoryReservation = Math.round(memBytes * 0.5); // soft limit = 50%
+        }
+        if (userConfig.resources.cpus) {
+          containerConfig.HostConfig.NanoCpus = Math.round(userConfig.resources.cpus * 1e9);
+        }
+      }
+
       try {
         log.info('docker', 'Pulling image', { image: processedTemplate.docker.image });
         await docker.pull(processedTemplate.docker.image);