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.

dankclaw/caddy/env.example

@@ -0,0 +1,7 @@
+# Caddy environment (placeholders only). The deploy writes the live file at
+# /home/dank/Containers/caddy/env from the checkout's .env; the quadlet reads
+# it via EnvironmentFile. Consumed by the Caddyfile's acme_dns block
+# (DNS-01 wildcard cert issuance). PORKBUN_API_SECRET_KEY is the name the
+# caddy-dns/porkbun module expects.
+PORKBUN_API_KEY=changeme
+PORKBUN_API_SECRET_KEY=changeme

dankclaw/caddy/quadlet/caddy.container

@@ -0,0 +1,54 @@
+# Quadlet unit: canonical Caddy reverse proxy + ACME (rootless, boot-persistent).
+#
+# Install path on dankclaw: ~/.config/containers/systemd/caddy.container
+# Unit name: caddy.service (container name: caddy)
+#
+# The homelab's single Caddy: it fronts every service on both hosts and issues
+# Let's Encrypt wildcard certs via DNS-01 (Porkbun). It left compose.yaml on
+# 2026-08-26 after a reboot exposed that the bare compose container never came
+# back: rootless Podman has no boot-time auto-start for bare containers, and
+# `restart: unless-stopped` does not survive the explicit stop that shutdown
+# performs. See AGENTS.md "Boot Persistence & Self-Healing" and
+# docs/Infrastructure/Caddy.md.
+#
+# It joins the existing compose network (dankclaw_default) so the Caddyfile's
+# container-name upstreams (authentik-server, grafana, ...) still resolve; if
+# no compose service has created that network yet at boot, quadlet creates it
+# first and compose reuses it by name later. The image is built locally from
+# dankclaw/caddy/Containerfile and exists only on this host, so Pull=never: a
+# boot must not stall on a registry that does not have it. Porkbun credentials
+# come from /home/dank/Containers/caddy/env (deploy writes it from the
+# checkout's .env; secrets never enter the repo).
+
+[Unit]
+Description=Caddy reverse proxy + ACME (Porkbun DNS-01) container
+After=network-online.target
+Wants=network-online.target
+
+[Container]
+ContainerName=caddy
+Image=franksdank/caddy-porkbun:latest
+Pull=never
+Network=dankclaw_default
+PublishPort=0.0.0.0:80:80/tcp
+PublishPort=0.0.0.0:443:443/tcp
+EnvironmentFile=/home/dank/Containers/caddy/env
+Volume=/home/dank/Containers/caddy/Caddyfile:/etc/caddy/Caddyfile:ro
+Volume=/home/dank/Containers/caddy/data:/data
+Volume=/home/dank/Containers/caddy/config:/config
+# The homepage: the host's /srv/homepage (deploy-managed, not the repo's
+# shared/homepage).
+Volume=/srv/homepage:/srv/homepage:ro
+# The bare-IP catch-all answers 302 (curl -f passes on <400); this proves
+# Caddy itself is serving without touching any upstream.
+HealthCmd=curl -sf -o /dev/null http://localhost:80/
+HealthInterval=30s
+HealthTimeout=10s
+HealthRetries=3
+
+[Service]
+Restart=always
+RestartSec=5
+
+[Install]
+WantedBy=default.target