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/events.js

@@ -0,0 +1,111 @@
+const express = require('express');
+
+/**
+ * Server-Sent Events route factory
+ * Pushes real-time updates to connected dashboard clients
+ * @param {Object} deps - Dependencies
+ * @param {Object} deps.resourceMonitor - Container resource monitor
+ * @param {Object} deps.healthChecker - Health checker
+ * @param {Object} deps.updateManager - Update manager
+ * @param {Function} deps.logError - Error logging function
+ * @returns {express.Router}
+ */
+module.exports = function({ resourceMonitor, healthChecker, updateManager, logError }) {
+  const router = express.Router();
+  const clients = new Set();
+
+  function broadcast(event, data) {
+    const msg = `event: ${event}\ndata: ${JSON.stringify(data)}\n\n`;
+    for (const res of clients) {
+      try { res.write(msg); } catch (_) { clients.delete(res); }
+    }
+  }
+
+  // --- Wire up EventEmitter listeners ---
+
+  // Resource monitor events
+  if (resourceMonitor) {
+    resourceMonitor.on('alert', (data) => {
+      broadcast('resource-alert', data);
+    });
+    resourceMonitor.on('auto-restart', (data) => {
+      broadcast('auto-restart', data);
+    });
+  }
+
+  // Health checker events
+  if (healthChecker) {
+    healthChecker.on('status-check', (data) => {
+      broadcast('status-change', {
+        serviceId: data.serviceId,
+        name: data.name,
+        status: data.status,
+        responseTime: data.responseTime,
+        timestamp: data.timestamp
+      });
+    });
+    healthChecker.on('incident-created', (data) => {
+      broadcast('incident', { type: 'created', ...data });
+    });
+    healthChecker.on('incident-resolved', (data) => {
+      broadcast('incident', { type: 'resolved', ...data });
+    });
+  }
+
+  // Update manager events
+  if (updateManager) {
+    updateManager.on('update-available', (data) => {
+      broadcast('update-available', data);
+    });
+    updateManager.on('update-start', (data) => {
+      broadcast('update-start', data);
+    });
+    updateManager.on('update-complete', (data) => {
+      broadcast('update-complete', data);
+    });
+    updateManager.on('update-failed', (data) => {
+      broadcast('update-failed', data);
+    });
+    updateManager.on('auto-update-start', (data) => {
+      broadcast('auto-update-start', data);
+    });
+    updateManager.on('auto-update-complete', (data) => {
+      broadcast('auto-update-complete', data);
+    });
+  }
+
+  // SSE endpoint
+  router.get('/stream', (req, res) => {
+    res.writeHead(200, {
+      'Content-Type': 'text/event-stream',
+      'Cache-Control': 'no-cache',
+      'Connection': 'keep-alive',
+      'X-Accel-Buffering': 'no',
+    });
+
+    // Send initial connected event
+    res.write(`event: connected\ndata: ${JSON.stringify({ clients: clients.size + 1 })}\n\n`);
+
+    clients.add(res);
+
+    // Heartbeat every 30s
+    const heartbeat = setInterval(() => {
+      try { res.write(': heartbeat\n\n'); } catch (_) { cleanup(); }
+    }, 30000);
+
+    function cleanup() {
+      clearInterval(heartbeat);
+      clients.delete(res);
+    }
+
+    req.on('close', cleanup);
+    req.on('error', cleanup);
+  });
+
+  // Client count (useful for debugging)
+  router.get('/clients', (req, res) => {
+    res.json({ success: true, count: clients.size });
+  });
+
+  return router;
+};