caddy + pihole: make both boot-persistent and self-healing

Caddy left compose.yaml for a quadlet unit (caddy.service): joins
dankclaw_default for container-name upstreams, Pull=never for the local-only
image, Porkbun credentials via /home/dank/Containers/caddy/env written by
deploy from .env, bare-IP-catch-all health check. deploy_caddy installs,
enables, and starts the unit after retiring the bare container (state is in
host volumes).

Pi-hole: the repo now owns the sysctl drop-in
(dankclaw/pihole/sysctl/99-dnsmasq.conf, ip_unprivileged_port_start=53);
deploy_pihole installs it to /etc/sysctl.d/, stages conflicting later-sorted
drop-ins in the home trash, and applies 'sysctl --system' (the boot code
path). This fixes the 2026-08-26 crash loop (port-53 bind denied, restart
counter 1645) caused by a second drop-in resetting the value to 80.

Tests: new caddy_quadlet.bats seam; caddyfile/deployment_flow assertions
repointed from the removed compose service to the quadlet; pihole.bats pins
the sysctl drop-in and its deployment; test-changed.sh routes dankclaw/caddy/
and the pihole subtree to their seams. Docs: Caddy, Pi-hole, Dankclaw Stack,
work log.

docs/Dankclaw/Dankclaw Stack.md

@@ -55,9 +55,9 @@ repo owns their scripts, units, and knowledge base (see
 
 ## Boot Persistence
 
-The Gitea database and server, the SearXNG trio (gluetun, searxng, valkey), and open-webui run as Quadlet units, so they start at boot. Gitea's web UI is reverse-proxied by the canonical Caddy compose service; the former standalone Gitea Caddy unit is retired. User linger is on. ComfyUI runs as a systemd unit around a bare process. The remaining services in the table are defined in `compose.yaml` and are not yet boot-persistent.
+The Gitea database and server, the SearXNG trio (gluetun, searxng, valkey), open-webui, Pi-hole, and Caddy run as Quadlet units, so they start at boot. Caddy left `compose.yaml` on 2026-08-26 after a reboot exposed that bare compose containers never come back; see [[Caddy]] for the unit and the incident. The former standalone Gitea Caddy unit is retired. User linger is on. ComfyUI runs as a systemd unit around a bare process. The remaining services in the table are defined in `compose.yaml` and are not yet boot-persistent — per AGENTS.md (Boot Persistence & Self-Healing) they each need a quadlet before they may be considered reliably deployed.
 
-Deploy the SearXNG trio with `scripts/deploy-searxng-quadlet.sh dankclaw` and open-webui with `scripts/deploy-open-webui-quadlet.sh dankclaw`. The Gitea units install to `~/.config/containers/systemd/` (see [[Gitea]]); Caddy is deployed through `scripts/deploy.sh dankclaw --service caddy`.
+Deploy the SearXNG trio with `scripts/deploy-searxng-quadlet.sh dankclaw`, open-webui with `scripts/deploy-open-webui-quadlet.sh dankclaw`, and Pi-hole with `scripts/deploy-pihole-quadlet.sh dankclaw`. The Gitea units install to `~/.config/containers/systemd/` (see [[Gitea]]); Caddy is deployed through `scripts/deploy.sh dankclaw --service caddy`.
 
 ## Routing Rules