[grade=B] DC-100: Service discovery — auto-detect running containers

GET /api/v1/discover scans running Docker containers, matches images
against 20 known patterns (Plex, Jellyfin, Sonarr, Radarr, qBittorrent,
Gitea, Nextcloud, Redis, Postgres, etc.), and returns suggested service
configs. Marks services already in the dashboard as 'existing'.

Returns: container ID, name, image, suggested type/name/port/protocol,
port mappings, labels, and existing flag. 5 tests, 1623 total pass.

dashcaddy-api/src/app.js

@@ -61,6 +61,7 @@ const updatesRoutes = require('../routes/updates');
 const authRoutes = require('../routes/auth');
 const shareRoutes = require('../routes/share');
 const i18nRoutes = require('../routes/i18n');
+const discoverRoutes = require('../routes/discover');
 const configRoutes = require('../routes/config');
 const dnsRoutes = require('../routes/dns');
 const notificationRoutes = require('../routes/notifications');
@@ -599,6 +600,13 @@ async function createApp() {
 
   // DC-077: i18n — language metadata and translations (public, no auth needed)
   apiRouter.use(i18nRoutes());
+
+  // DC-100: Service discovery — auto-detect running containers
+  apiRouter.use(discoverRoutes({
+    docker: ctx.docker,
+    servicesStateManager: ctx.servicesStateManager,
+    asyncHandler: ctx.asyncHandler,
+  }));
   apiRouter.use(updatesRoutes({
     updateManager: ctx.updateManager,
     selfUpdater: ctx.selfUpdater,