[grade=B] DC-104: App catalog API — browse 38 curated templates

GET /api/v1/catalog — list all apps with category filter, sort options
GET /api/v1/catalog/search?q=plex — search by name/category
GET /api/v1/catalog/:appId — get app details (image, ports, env, volumes)

Uses existing app-templates.js (38 templates). Auto-categorizes into:
media, productivity, development, database, network, smart-home, monitoring.
Popular badges for Plex, Jellyfin, Sonarr, Radarr, Nextcloud, Gitea, qBittorrent.

Auth required (behind login). 1633 tests pass.

dashcaddy-api/src/app.js

@@ -63,6 +63,7 @@ const shareRoutes = require('../routes/share');
 const i18nRoutes = require('../routes/i18n');
 const discoverRoutes = require('../routes/discover');
 const discoverAdoptRoutes = require('../routes/discover-adopt');
+const catalogRoutes = require('../routes/catalog');
 const configRoutes = require('../routes/config');
 const dnsRoutes = require('../routes/dns');
 const notificationRoutes = require('../routes/notifications');
@@ -618,6 +619,12 @@ async function createApp() {
     siteConfig: ctx.config,
     asyncHandler: ctx.asyncHandler,
   }));
+
+  // DC-104: App catalog — browse curated templates
+  apiRouter.use(catalogRoutes({
+    APP_TEMPLATES: require('./docker/app-templates'),
+    asyncHandler: ctx.asyncHandler,
+  }));
   apiRouter.use(updatesRoutes({
     updateManager: ctx.updateManager,
     selfUpdater: ctx.selfUpdater,