feat(llm-inference): move astro-orbiter monitoring to GitOps (values.yaml + dashboards.yaml)

- Prometheus scrape configs for node/gpu/llama-server exporters on
  astro-orbiter now declared in cluster/applications/monitoring/values.yaml
  (additionalScrapeConfigs), applied via ArgoCD sync instead of an
  imperative kubectl secret patch from the Ansible role.
- Grafana dashboard for astro-orbiter LLM inference added as a ConfigMap
  in cluster/applications/monitoring/dashboards.yaml (grafana_dashboard=1
  sidecar label), replacing the role's ad-hoc kubectl apply of a rendered
  Jinja template.
- ansible/roles/llm-inference/tasks/monitoring.yml: removed the kubectl
  get/patch/apply tasks and orphaned grafana-llm-dashboard.json.j2
  template; role now only stands up node_exporter + nvidia_gpu_exporter
  and verifies they're reachable — cluster-facing config lives in Git.
- host_vars/vars.yml + inventory.yml: finalize astro-orbiter as the
  llama.cpp/RTX 3090 host (jarvis user, ssh key), drop stale Ollama/AMD
  vars and ollama_server inventory group superseded by the ATX rebuild.

ansible/inventory.yml

@@ -59,13 +59,6 @@ n8n_server:
   hosts:
     tiki-room:
 
-ollama_server:
-  hosts:
-    astro-orbiter:
-      ansible_host: 10.1.71.130
-      ansible_user: wed
-      ansible_become: true
-
 astro_orbiter:
   hosts:
     astro-orbiter:
@@ -76,6 +69,7 @@ hermes_server:
       ansible_host: 10.1.71.131
       ansible_user: wed
       ansible_become: true
+      ansible_ssh_private_key_file: ~/.ssh/ansible
 
 honcho_server:
   hosts: