feat(observability): per-container metrics via cadvisor + Containers dashboard

Per-container CPU/memory was invisible for the quadlet app stack — Grafana could
only see the host (node_exporter) and the LLM engines. This adds a rootless
cadvisor quadlet on each host and a `containers` dashboard.

cadvisor works on this rootless-Podman / cgroup-v2 host on one condition:
--cgroupns=host. Podman starts every container in a private cgroup namespace, so
without it cadvisor sees only its own cgroup root and exports a single series
(measured 2026-10-20: 1 series off, 996 on). The libpod socket does not name the
rootless app containers (it resolved 2 of 34), so naming comes from elsewhere:
the quadlet unit name is carried in the cgroup path
(app.slice/<name>.service/libpod-payload-<hex>), and Prometheus relabels it into
a `container` label. No podman socket needed.

cadvisor cannot bind per-interface like node_exporter, so each unit is a bridge
container publishing exactly 127.0.0.1:8080 and the host LAN address — never a
wildcard. Prometheus (a bridge container) reaches a host-published port at the
LAN address, so cadvisor-dankclaw/dankserver scrape 192.168.0.143:8080 /
192.168.0.235:8080. Only the families cadvisor actually exports for these
containers are graphed — CPU usage, memory working-set/limit, OOM — not network
or filesystem, which are absent under the host-PID layout.

Wired through the deployer (allowlist, deploy_observability case + /healthz gate,
dispatcher), the planner (both targets), and observability_quadlet.bats.

serverAppConfigs-docs/Infrastructure/Observability.md

@@ -10,9 +10,9 @@ timestamp: 2026-10-20
 
 ## Summary
 
-Six containers and one host-side process: Prometheus (metrics), Grafana
+Seven containers and one host-side process: Prometheus (metrics), Grafana
 (dashboards), Loki (log store), Alloy (log shipper), node-exporter (host
-metrics) and Alertmanager (alert delivery), with `signal-relay` on the host
+metrics), cadvisor (per-container metrics) and Alertmanager (alert delivery), with `signal-relay` on the host
 carrying every firing group to Signal. All of it is Quadlet-managed,
 boot-persistent and loopback-only, deployed by
 `scripts/deploy-remote.sh` → `deploy_observability`. The metrics half works
@@ -34,6 +34,7 @@ that proves it today.
 | Loki | `localhost/franksdank/loki:latest` | `127.0.0.1:3100` | `loki.container` | [[Loki]] |
 | Alloy | `localhost/franksdank/alloy:latest` | `127.0.0.1:12345` | `alloy.container` | [[Alloy]] |
 | node-exporter | `docker.io/prom/node-exporter:latest` | host netns: `127.0.0.1:9100` + `192.168.0.143:9100` | `node-exporter.container` | [[Node-Exporter]] |
+| cadvisor | `gcr.io/cadvisor/cadvisor:v0.49.1` | bridge publish `127.0.0.1:8080` + `192.168.0.143:8080` | `cadvisor.container` | — |
 | Signal relay | host `python3`, not a container | `192.168.0.143:18093` | `scripts/signal-relay.service` (user unit) | [[Alertmanager]] |
 
 Every unit lives in `dankclaw/observability/quadlet/`, carries
@@ -44,9 +45,10 @@ linger is on for `dank`). `signal-relay.service` reports `enabled` + `active`
 the same day, and `homepage-status.timer` — the root unit that probes all of
 these on loopback — is `enabled` + `active` (`deploy-remote.sh:319-321` copies
 the probe registry `shared/homepage/services.json` to `/srv/homepage`).
-Dankserver runs one member of this family, node-exporter, as its own unit
-(`dankserver/observability/quadlet/node-exporter.container`, `generated` +
-`active`, binding `127.0.0.1:9100` + `192.168.0.235:9100`).
+Dankserver runs two members of this family, node-exporter and cadvisor, as
+its own units (`dankserver/observability/quadlet/{node-exporter,cadvisor}.container`,
+`generated` + `active`; node-exporter binds `127.0.0.1:9100` + `192.168.0.235:9100`,
+cadvisor publishes `127.0.0.1:8080` + `192.168.0.235:8080`).
 
 ## Exposure
 
@@ -98,10 +100,23 @@ verify it through the APIs.
   relay, and `journalctl --user -u signal-relay` records successful
   `sent to +12062476336:` lines for every rule in the set.
 * **Dashboards: working.** Provisioned datasources — Prometheus (uid
-  `prometheus`) and Loki (uid `loki`) — and the `llm-fleet` dashboard, all
+  `prometheus`) and Loki (uid `loki`) — and the `llm-fleet`, `host-system`,
+  `containers`, `observability` and `logs-overview` dashboards, all
   installed from `shared/grafana/provisioning/`. The Loki datasource is how
   you read logs: Loki has no web UI of its own, so Grafana Explore is the
   human surface (the guarded `loki.franksdank.cloud` vhost serves only the API).
+* **Per-container metrics: the `containers` dashboard (added 2026-10-20; live
+  after `deploy.sh <host> --service cadvisor`).** cadvisor is the only way to see
+  per-container CPU/memory here, and on this rootless-Podman host it works on one
+  condition: `--cgroupns=host`. Podman starts every container in a PRIVATE cgroup
+  namespace, so without that flag cadvisor sees only its own cgroup root and
+  exports a single series (measured 2026-10-20: 1 series off, 996 on). cadvisor
+  names nothing itself — the libpod socket resolved only 2 of 34 rootless
+  containers — but the quadlet unit name is carried in the cgroup path
+  (`app.slice/<name>.service/…`), so `prometheus.yml` relabels that path into a
+  `container` label. Network and filesystem are NOT exported for these containers
+  (no netns/classid attribution under the host-PID layout), so the dashboard
+  graphs only CPU, memory and OOM and does not fake the rest.
 * **Logs: fixed in code, awaiting deploy.** The pipeline shipped nothing because
   a rootless Alloy cannot read the `0640` journal files, and the container-log
   globs point at a root-storage layout that does not exist here. The fix is built
@@ -117,7 +132,7 @@ verify it through the APIs.
 
 ## Citations
 
-- `dankclaw/observability/quadlet/{prometheus,alertmanager,grafana,loki,alloy,node-exporter}.container`
+- `dankclaw/observability/quadlet/{prometheus,alertmanager,grafana,loki,alloy,node-exporter,cadvisor}.container`
 - `scripts/deploy-remote.sh:219-300` (copiers + relay), `:521-536` (health waits), `:477-486` (grafana env seed)
 - `scripts/signal-relay.py:26-49`, `scripts/signal-relay.service`
 - `shared/prometheus/prometheus.yml`, `shared/prometheus/alertmanager.yml`, `shared/prometheus/rules/llm-fleet.yml`