fix: SNMP status table no longer vanishes after back/return navigation (v0.11.9 Beta)

Root cause: backend filtered switches by status='online', so a mid-poll-cycle
device (briefly 'unknown') caused the endpoint to return [] — and the frontend
rendered nothing when the array was empty.

- Backend: query ALL switch devices (not just online ones); unreachable devices
  already fall through to the Promise.allSettled error path and render with an
  error badge, so no data is lost
- Frontend: replace silent `length > 0 &&` guard with a three-way ternary that
  shows a "No managed switches found" message when the array is empty, so the
  user always sees feedback instead of a blank section
- Frontend: add staleTime: 60_000 to the SNMP query to prevent the hair-trigger
  background refetch that raced with the poller on every navigation

backend/package.json

@@ -1,6 +1,6 @@
 {
   "name": "mikrotik-manager-backend",
-  "version": "0.11.8-beta",
+  "version": "0.11.9-beta",
   "description": "Mikrotik Network Management Platform - Backend API",
   "main": "dist/index.js",
   "scripts": {

backend/src/routes/switches.ts

@@ -101,10 +101,12 @@ router.put('/lldp', requireWrite, async (req: Request, res: Response) => {
   });
 });
 
-// GET /api/switches/snmp — SNMP config/status per online switch
+// GET /api/switches/snmp — SNMP config/status for all managed switches
+// Includes offline/unknown devices so the list never disappears during a poll cycle.
+// Unreachable devices fall through to the Promise.allSettled error path and render with an error note.
 router.get('/snmp', async (_req: Request, res: Response) => {
   const switches = await query<DeviceRow>(
-    `SELECT * FROM devices WHERE device_type = 'switch' AND status = 'online'`
+    `SELECT * FROM devices WHERE device_type = 'switch' ORDER BY name`
   );
 
   const results = await Promise.allSettled(