[grade=B] DC-107: Disaster recovery — one-click full backup + restore

3 endpoints:
- POST /api/v1/disaster/backup — complete snapshot (services, config, credentials,
  Caddyfile, DNS creds, themes, logo, favicon) as downloadable JSON with SHA-256 checksum
- POST /api/v1/disaster/restore — restore from uploaded snapshot with checksum verification
- GET  /api/v1/disaster/status — last backup/restore status

Checksum verification prevents restoring corrupted snapshots.
Partial restore mode continues on per-file errors.
1633 tests pass.

dashcaddy-api/src/app.js

@@ -65,6 +65,7 @@ const discoverRoutes = require('../routes/discover');
 const discoverAdoptRoutes = require('../routes/discover-adopt');
 const catalogRoutes = require('../routes/catalog');
 const wizardRoutes = require('../routes/wizard');
+const disasterRoutes = require('../routes/disaster-recovery');
 const configRoutes = require('../routes/config');
 const dnsRoutes = require('../routes/dns');
 const notificationRoutes = require('../routes/notifications');
@@ -632,6 +633,14 @@ async function createApp() {
     APP_TEMPLATES: require('./docker/app-templates'),
     asyncHandler: ctx.asyncHandler,
   }));
+
+  // DC-107: Disaster recovery — full backup + restore
+  apiRouter.use(disasterRoutes({
+    servicesStateManager: ctx.servicesStateManager,
+    platformPaths: require('../platform-paths'),
+    log: ctx.log,
+    asyncHandler: ctx.asyncHandler,
+  }));
   apiRouter.use(updatesRoutes({
     updateManager: ctx.updateManager,
     selfUpdater: ctx.selfUpdater,