fix: gitea boot persistence via quadlet (incident 2026-08-16)

unattended-upgrades rebooted dankclaw at 15:01; the legacy
podman-compose gitea stack had no systemd units, so rootless podman
did not auto-start the containers. Gitea was down ~1 hour.

- add quadlet units (dankclaw/gitea/quadlet/): gitea-postgres,
  gitea-server, gitea-caddy + gitea.network (DNS enabled; the default
  rootless podman network has dns_enabled=false)
- add gitea stack Caddyfile (upstream gitea-server:3000) and
  .env.example; live password stays in /opt/gitea/.env (0600)
- fix latent name bugs in main stack config: DATABASE_HOST
  gitea-postgres, Caddyfile upstream gitea-server
- docs: rewrite Gitea page for the quadlet stack (management, boot
  persistence, secrets, gotchas, incident log); fix port 3000 in
  stack table; Postgres connection notes
- legacy compose retired on target to /opt/gitea/.deprecated/

dankclaw/gitea/quadlet/gitea-postgres.container

@@ -0,0 +1,31 @@
+# Quadlet unit: Gitea PostgreSQL (rootless, boot-persistent).
+#
+# Install path on dankclaw: ~/.config/containers/systemd/gitea-postgres.container
+# Unit name: gitea-postgres.service (podman 5.x drops the container- prefix)
+#
+# The DB password lives in /opt/gitea/.env on the host (mode 0600).
+# This file holds no secrets. See docs/Dankclaw/Gitea.md.
+# The [Service] EnvironmentFile= line lets systemd expand
+# ${GITEA_DB_PASSWORD} in the generated ExecStart.
+
+[Unit]
+Description=Gitea PostgreSQL container
+After=network.target
+
+[Container]
+ContainerName=gitea-postgres
+Network=gitea.network
+Image=docker.io/library/postgres:16-alpine
+EnvironmentFile=/opt/gitea/.env
+Environment=POSTGRES_USER=gitea
+Environment=POSTGRES_PASSWORD=${GITEA_DB_PASSWORD}
+Environment=POSTGRES_DB=gitea
+Volume=/opt/gitea/data/gitea-postgres:/var/lib/postgresql/data
+
+[Service]
+EnvironmentFile=/opt/gitea/.env
+TimeoutStartSec=900
+Restart=always
+
+[Install]
+WantedBy=default.target