Bump Frigate retention and add recording health check

Increase retention: continuous 3→180d, detections 14→30d, alerts 30→730d.
Plenty of NFS headroom (~9.4 TiB free, ~6.6 GB/day for one camera).

Add frigate-recording check to services-check that verifies camera_fps > 0,
which would have caught the 6-day outage from the mqtt config removal.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

argocd/manifests/frigate/frigate-config.yml

@@ -70,14 +70,14 @@ model:
 record:
   enabled: true
   continuous:
-    days: 3
+    days: 180
   alerts:
     retain:
-      days: 30
+      days: 730
       mode: active_objects
   detections:
     retain:
-      days: 14
+      days: 30
       mode: motion
 
 snapshots: