docs: Pi-hole KB page + dnsmasq retirement across the vault

- new docs/Infrastructure/Pi-hole.md (quadlet, records, upstream, web UI,
  failure modes incl. the rootless /etc/hosts single-label echo)
- LAN-DNS.md: Pi-hole quadlet section, router hand-off, host DNS
- Network Architecture / Caddy / Homepage / index / AGENTS.md: name swap

AGENTS.md

@@ -11,8 +11,8 @@ one checkout per host, one deploy script.
   `frank-default-small` LLM service.
 - **Dankclaw** (192.168.0.143) — AI/search/development/observability stack
   (SearXNG via Gluetun, ComfyUI, OpenWebUI, Hermes, Gitea, Grafana, Prometheus,
-  Loki, Alloy) plus the `frank-default-large` LLM service. Caddy on Dankclaw
-  reverse-proxies both hosts.
+  Loki, Alloy, Pi-hole) plus the `frank-default-large` LLM service. Caddy on
+  Dankclaw reverse-proxies both hosts.
 
 **2026-08-22 merge:** the former `vllmScripts` repository (LLM fleet scripts,
 units, env tunables, and runbook) is merged into this repo. Its full git