docs(observability): record the quadlet cutover, the exposure posture, and the unconfigured state

Rewrites the [[Observability]] umbrella page and the five component pages for
what is actually deployed: rootless Quadlet units instead of compose services,
the loopback-only publish posture (node-exporter's LAN binding explained), the
loki healthcheck living in its image because the image has no shell, and the
Home=/root trap that killed the first grafana start.

Adds the note that matters most to a reader: the stack is installed, healthy
and UNCONFIGURED. Grafana reports zero datasources and zero dashboards with an
empty provisioning directory; Prometheus has no rule files and no Alertmanager;
Loki is configured but has no reader; node-exporter runs its default
collectors. Alloy is the only configured piece. Metrics and logs are collected
and retained, and nothing is visualized or alerted on.

AGENTS.md's boot-persistence gap note is replaced by the resolution.

serverAppConfigs-docs/index.md

@@ -84,9 +84,9 @@ covers both workloads).
 - [[authentik-worker]] — Authentik background worker service
 - [[Homepage]] — password-protected service index
 - [[Homepage Design Grilling]] — homepage decision log and open questions
-- [[Observability]] — Grafana, Prometheus, Loki, Alloy
-- [[Grafana]] — dashboards
-- [[Prometheus]] — metrics collection
+- [[Observability]] — Grafana, Prometheus, Loki, Alloy, node-exporter: the stack, its quadlet deployment, its exposure, and **what is still unconfigured**
+- [[Grafana]] — dashboards (no datasource or dashboard configured yet)
+- [[Prometheus]] — metrics collection (no alerting rules or Alertmanager)
 - [[Node-Exporter]] — host metrics
 - [[Loki]] — log storage
 - [[Alloy]] — log shipping (replaces Promtail)