Authentik SSO + homepage naked domain

Auth layer (Authentik 2026.8.0):
- compose: 3-service stack (authentik-postgres, authentik-server, authentik-worker),
  postgres health-gated, bind mounts under /home/dank/authentik
- Caddyfile: auth.franksdank.cloud vhost; forward_auth on the no-auth vhosts
  (homepage, SearXNG, Hermes, Prometheus, RomM, Copyparty); outpost path
  proxied first in a route block
- .env.example: AUTHENTIK_PG_PASS + AUTHENTIK_SECRET_KEY
- deploy.sh: render only CADDY_BASICAUTH_HASH (the homepage per-user hashes
  are retired; grafana + pihole keep basicauth)
- tests/authentik.bats (new) + updated homepage/caddyfile/pihole seams
- docs: Authentik.md + per-service pages; Caddy.md + Homepage.md updated

Homepage (naked domain):
- Caddyfile: dankclaw.franksdank.cloud -> franksdank.cloud www.franksdank.cloud;
  dankclaw + dankserver redirect to it; bare-IP catch-all updated
- addn-hosts: A records for the naked domain, www, and auth (all -> 143)
- tests/pihole.bats: vhost_names handles multi-address blocks; TLD check
  allows the naked domain

All 146 tests pass.

docs/Infrastructure/authentik-postgres.md

@@ -0,0 +1,14 @@
+# authentik-postgres
+
+The PostgreSQL 16 database for [Authentik](Authentik.md) — the homelab's SSO /
+OIDC provider. It is the only stateful store in the stack (users, flows,
+sessions, events). Redis was removed in Authentik 2025.10; sessions and caching
+now live here.
+
+- **Compose service:** `authentik-postgres` (in `dankclaw/compose.yaml`)
+- **Image:** `docker.io/library/postgres:16-alpine`
+- **Data:** `/home/dank/authentik/postgres` (bind mount; no named volumes)
+- **Health:** `pg_isready -d authentik -U authentik`
+
+See [Authentik.md](Authentik.md) for the full architecture, setup, backups
+(`pg_dump`), and failure modes.