v-m: alerts: Add durations to spammy alerts

Let's avoid sending alerts immediately when something is unavailable,
because the issue might be transient and will resolve itself shortly.

victoria-metrics/alerts.yml

@@ -18,6 +18,7 @@ groups:
   - alert: NUT is offline
     expr: >-
       absent(collectd_nut_percent)
+    for: 10m
 
 - name: Bitwarden
   rules:
@@ -120,9 +121,11 @@ groups:
   - alert: Frigate is Unavailable
     expr:
       homeassistant_entity_available{entity=~".*frigate_(server|status)"} != 1
+    for: 10m
   - alert: Camera unavailable
     expr:
       homeassistant_entity_available{domain="camera"} != 1
+    for: 10m
 
 - name: Sensors
   rules: