fix(observability): 🐛 enable vmagent, fix grafana auth, disable vmauth on dev

- Enable VMAgent (was disabled → no metrics scraped)
- Remove disable_login from Grafana config; add security block so operator can auth via API
- Disable VMAuth (invalid trailing-dot hostname o12y.observability.; not needed on dev)

otc/dev.t09.de/stacks/observability/victoria-k8s-stack/values.yaml

@@ -673,7 +673,7 @@ vmalert:
 
 vmauth:
   # -- Enable VMAuth CR
-  enabled: true
+  enabled: false
   # -- VMAuth annotations
   annotations: {}
   # -- (object) Full spec for VMAuth CRD. Allowed values described [here](https://docs.victoriametrics.com/operator/api#vmauthspec)
@@ -696,7 +696,7 @@ vmauth:
 
 vmagent:
   # -- Create VMAgent CR
-  enabled: false
+  enabled: true
   # -- VMAgent annotations
   annotations: {}
   # -- Remote write configuration of VMAgent, allowed parameters defined in a [spec](https://docs.victoriametrics.com/operator/api#vmagentremotewritespec)