Add auto-update system for DashCaddy instances

- self-updater.js: polls for new versions, downloads/verifies tarballs,
  triggers host-side rebuild via systemd path unit
- dashcaddy-update.sh + systemd units: host-side container rebuild with
  automatic rollback on health check failure
- 7 new /api/v1/system/* endpoints for version info, update check/apply,
  rollback, and update history
- Frontend: DashCaddy tab in Updates modal with version display,
  changelog, update button, rollback, and notification dot
- install.sh: updater service installation, volume mounts, env vars
- build-release.sh + webhook-handler.js: release server pipeline
  (Gitea webhook → build tarball → deploy to get.dashcaddy.net)
- Dockerfile: DASHCADDY_COMMIT build arg → VERSION file
- Version bump to 1.1.0

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

dashcaddy-api/server.js

@@ -49,6 +49,7 @@ const resourceMonitor = require('./resource-monitor');
 const backupManager = require('./backup-manager');
 const healthChecker = require('./health-checker');
 const updateManager = require('./update-manager');
+const selfUpdater = require('./self-updater');
 const StateManager = require('./state-manager');
 const auditLogger = require('./audit-logger');
 const portLockManager = require('./port-lock-manager');
@@ -1160,7 +1161,7 @@ Object.assign(ctx, {
   app, siteConfig, servicesStateManager, configStateManager,
   credentialManager, authManager, licenseManager,
   healthChecker, updateManager, backupManager, resourceMonitor,
-  auditLogger, portLockManager,
+  auditLogger, portLockManager, selfUpdater,
   APP_TEMPLATES, TEMPLATE_CATEGORIES, DIFFICULTY_LEVELS, RECIPE_TEMPLATES, RECIPE_CATEGORIES,
   asyncHandler, errorResponse, ok, fetchT, log, logError, safeErrorMessage,
   buildDomain, buildServiceUrl, getServiceById, readConfig, saveConfig, addServiceToConfig,
@@ -1863,6 +1864,26 @@ const server = app.listen(PORT, '0.0.0.0', () => {
   } catch (error) {
     log.error('server', 'Update manager failed to start', { error: error.message });
   }
+
+  try {
+    selfUpdater.start();
+    log.info('server', 'Self-updater started', { interval: selfUpdater.config.checkInterval, url: selfUpdater.config.updateUrl });
+    // Check for post-update result (did a previous update succeed or roll back?)
+    selfUpdater.checkPostUpdateResult().then(result => {
+      if (result) {
+        log.info('server', 'Post-update result', result);
+        if (typeof ctx.notification?.send === 'function') {
+          ctx.notification.send('system.update',
+            result.success ? 'DashCaddy Updated' : 'DashCaddy Update Failed',
+            result.success ? `Updated to v${result.version}` : `Update failed: ${result.error || 'Unknown'}. Rolled back.`,
+            result.success ? 'info' : 'error'
+          );
+        }
+      }
+    }).catch(() => {});
+  } catch (error) {
+    log.error('server', 'Self-updater failed to start', { error: error.message });
+  }
   
   // Tailscale API sync (if OAuth configured)
   if (tailscaleConfig.oauthConfigured) {
@@ -1881,6 +1902,7 @@ function shutdown(signal) {
   backupManager.stop();
   healthChecker.stop();
   updateManager.stop();
+  selfUpdater.stop();
   stopTailscaleSyncTimer();
   server.close(() => {
     log.info('shutdown', 'HTTP server closed');