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  vars and ollama_server inventory group superseded by the ATX rebuild.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/roles/llm-inference/templates/llama-server.service.j2

@@ -15,7 +15,12 @@ ExecStart=/opt/llama.cpp/build/bin/llama-server \
     --ctx-size {{ llm_max_model_len }} \
     --n-gpu-layers {{ llm_gpu_layers }} \
     --parallel {{ llm_parallel_slots }} \
-    --chat-template gemma
+    --metrics
+# NOTE: no --chat-template flag — llama-server auto-detects and uses the
+# GGUF's own embedded Jinja chat template (verified correct Gemma-2
+# start_of_turn/end_of_turn format for bartowski's gemma-2-27b-it-Q4_K_M).
+# The built-in "--chat-template gemma" name does NOT match this model's
+# expected format on this llama.cpp build and produced garbled completions.
 Restart=on-failure
 RestartSec=10
 TimeoutStartSec=120