alerting: Alertmanager + Signal relay deliver firing rules to Frank's phone

- dankclaw/observability/quadlet/alertmanager.container: loopback :9093,
  config from shared/prometheus/alertmanager.yml, family conventions
- shared/prometheus/alertmanager.yml: single signal receiver, group_by
  alertname, 30s/5m/4h intervals, webhook to host.containers.internal:18093
- scripts/signal-relay.py + .service: host-side user unit, loopback :18093,
  15-min dedupe, sends via signal-cli account 318311
- prometheus.yml: alerting block to alertmanager:9093; stale comments fixed
- llm-fleet.yml: delivery header; LlmSpecDecodeOff annotation now drafter-agnostic
- deploy.sh/deploy-remote.sh/deploy-plan.py: alertmanager service, config
  copy, relay install, planner routing for config + relay files
- homepage: alertmanager status card (loopback probe)
- tests: alertmanager in UNITS/loopback/health/PAIRS/planner + five new
  delivery-path seams (webhook<->relay contract, prometheus target, relay
  unit, signal-cli account, planner routing)
- docs: Alertmanager.md component page, Observability.md, Prometheus.md,
  index.md, AGENTS.md delivery line

serverAppConfigs-docs/Infrastructure/Prometheus.md

@@ -16,7 +16,7 @@ Authentik; post-auth the Caddy vhost routes straight to `prometheus:9090`) —
 | Config | `/opt/prometheus/config/prometheus.yml`, installed from `shared/prometheus/prometheus.yml` on every deploy |
 | Data | `/opt/prometheus/data` (TSDB) |
 | Retention | `--storage.tsdb.retention.time=30d` |
-| Alerting | 5 alert rules + 1 recording rule (`shared/prometheus/rules/llm-fleet.yml`). Evaluated, **not delivered**: there is no Alertmanager (see [[Observability]]) |
+| Alerting | 5 alert rules + 1 recording rule (`shared/prometheus/rules/llm-fleet.yml`), evaluated **and delivered** since 2026-09-17: the `alerting:` block ships to `alertmanager:9093` → Signal relay → signal-cli (see [[Alertmanager]]) |
 
 ## Targets