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  vars and ollama_server inventory group superseded by the ATX rebuild.

cluster/applications/monitoring/values.yaml

@@ -212,6 +212,36 @@ prometheus:
       #         array: utilidor
       #         array_type: physical
 
+      # astro-orbiter — LLM inference host (Ryzen 7 5800XT / RTX 3090)
+      # Managed by roles/llm-inference (Phase monitoring). Three targets:
+      # node (system), gpu (nvidia_gpu_exporter), llama-server (inference metrics)
+      - job_name: node-astro-orbiter
+        scrape_interval: 30s
+        static_configs:
+          - targets:
+              - 10.1.71.130:9100
+            labels:
+              hostname: astro-orbiter
+
+      - job_name: gpu-astro-orbiter
+        scrape_interval: 15s
+        static_configs:
+          - targets:
+              - 10.1.71.130:9835
+            labels:
+              hostname: astro-orbiter
+              gpu: rtx3090
+
+      - job_name: llama-server-astro-orbiter
+        scrape_interval: 15s
+        metrics_path: /metrics
+        static_configs:
+          - targets:
+              - 10.1.71.130:8000
+            labels:
+              hostname: astro-orbiter
+              model: bartowski/gemma-2-27b-it-GGUF
+
 # ─── Grafana ──────────────────────────────────────────────────────────────────
 grafana:
   enabled: true