feat: version update check — notify when newer version is on GitHub (v0.11.8 Beta)

Backend: GET /api/system/version-check fetches frontend/package.json from
the main branch on GitHub, caches result in app_settings for 24 hours,
and compares semver against the running version. Fails silently (no banner)
for air-gapped or firewalled deployments.

Frontend: dismissible blue update banner in SecurityBanners (rendered
between TopBar and main content) — only visible when a newer version is
detected. Shows target version and docker compose update command.

backend/src/index.ts

@@ -47,6 +47,7 @@ import configTemplatesRoutes from './routes/configTemplates';
 import wirelessRoutes from './routes/wireless';
 import networkServicesRoutes from './routes/networkServices';
 import credentialPresetsRoutes from './routes/credentialPresets';
+import systemRoutes from './routes/system';
 import { auditMiddleware } from './middleware/auditMiddleware';
 
 const app = express();
@@ -217,6 +218,7 @@ app.use('/api/audit-log', auditLogRoutes);
 app.use('/api/tags', tagsRoutes);
 app.use('/api/maintenance-windows', maintenanceWindowsRoutes);
 app.use('/api/config-templates', configTemplatesRoutes);
+app.use('/api/system', systemRoutes);
 
 // ─── Error Handler ────────────────────────────────────────────────────────────
 app.use(errorHandler);