ops: add Prometheus + Grafana monitoring stack on CT 104

- Prometheus :9090, Grafana :9091, node-exporter :9100
- LiteLLM /metrics/ enabled via prometheus callback
- Scrapes: litellm (bearer auth), node-ct104, prometheus self
- 14 litellm_* metrics confirmed flowing
- Stack: /opt/stacks/monitoring; migrate to CT 109 ops when built

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

infra/portmap.md

@@ -8,6 +8,9 @@
 
 | Range | Category |
 |---|---|
+| 9090 | Prometheus (monitoring) |
+| 9091 | Grafana (monitoring) |
+| 9100 | node-exporter (host metrics) |
 | 10000–10999 | Infrastructure |
 | 11000–11999 | Security & Auth |
 | 12000–12999 | Media – Immich |
@@ -23,6 +26,19 @@
 
 ---
 
+## Monitoring (9090 / 9091 / 9100)
+
+| Port | Service | Container | Public URL | Notes |
+|---|---|---|---|---|
+| [9090](http://192.168.1.40:9090) | Prometheus | `prometheus` | — | LAN only; stack `/opt/stacks/monitoring` |
+| [9091](http://192.168.1.40:9091) | Grafana | `grafana` | `grafana.nuclide.systems` (Zoraxy route pending) | admin pw in `.env`; OIDC pending PocketID client |
+| 9100 | node-exporter | `node-exporter` | — | host-network mode; scrapes CT 104 |
+
+Scrape targets: `litellm` (`:14000/metrics/`, bearer `sk-tapirnase`), `node-ct104` (`:9100`), `prometheus` (`:9090`).  
+LiteLLM metrics enabled via `litellm_settings.callbacks: ["prometheus"]` in `ai/litellm-config/config.yaml`.
+
+---
+
 ## Infrastructure (10000–10999)
 
 | Port | Service | Container | Public URL | Notes |