Run the Sites as rootless Podman Quadlets, and build with podman

The fleet on emily is rootless Podman with Quadlet units under
~/.config/containers/systemd and state in ~/podman-data, all behind one shared
Caddy unit. This brings the menus in line instead of leaving them the last
Docker deployment. The build moves with them: podman reads a Containerfile as
readily as a Dockerfile, so the name now says which toolchain is real.

The app is one .container and one .network file. Two details carry it.
UserNS=keep-id maps the image's own node account onto the user that owns the
units, so data/ and site.env stay owned by tanshu: plain tar backups, no
subuids. provision-site-env.sh writes site.env with the same mapping rather
than --user, which under rootless Podman would have produced a subuid-owned
file the app could not read. And the Site registers its own network with Caddy
by writing a drop-in beside caddy.container, so Caddy never lists its upstreams
and never changes when a Site is added. The unit keeps the Docker-era container
name for the scripts and muscle memory that look it up, while the Caddyfile
proxies to a dotless NetworkAlias, because a container name with dots in it is
a liability in DNS.

The unit keeps podman's Pull=missing, so a restart or a reboot never depends on
the registry being reachable, while the play pulls explicitly at deploy time.
That is also where a missing `podman login` for the private registry now fails,
with the instruction, rather than as a unit that will not start.

copy-site-data.sh moves a Site's data across, and is not a plain rsync:
/var/lib/menu.* on monoco belongs to uid 1000 while the ssh user there is 1001,
so the read needs sudo; monoco cannot ssh to emily, so the workstation relays
the tar; and the extraction runs as tanshu on emily, which is what makes the
files land owned by the user keep-id maps the app onto. It proves the copy by
comparing a SHA-256 of the whole tree against the source and checking every
file's owner.

Not yet done: the copies themselves and the DNS move, which need a human.

ansible/vars/default.yml

@@ -2,19 +2,58 @@
 # Defaults shared by every Site. Each Site's own file is named by the `var_file`
 # in ansible/hosts, and its slug is its inventory name.
 
+# ---------------------------------------------------------------------------
+# Rootless Podman / Quadlet
+# ---------------------------------------------------------------------------
+# podman_user is derived from the connection: this play carries no become, so the
+# Quadlet units belong to whoever Ansible connects as. Requires gather_facts
+# (set in playbook.yml).
+#
+# These three duplicate caddy/vars/default.yml in the ansible-playbooks repo,
+# which owns the Caddy unit these Sites sit behind. Keep them in sync.
+podman_user: "{{ ansible_facts['user_id'] }}"
+podman_data_dir: "{{ ansible_facts['user_dir'] }}/podman-data"
+quadlet_dir: "{{ ansible_facts['user_dir'] }}/.config/containers/systemd"
+
 # Which Site config inside the image to run, and which web address it serves.
 site: '{{ inventory_hostname }}'
 
+# ---------------------------------------------------------------------------
+# The app
+# ---------------------------------------------------------------------------
 image_name: registry.tanshu.com/menu-admin
 image_tag: "{{ tag | default('latest') }}"
 
+# The unit file is menu-<site>.container and the Podman network is
+# menu-<site>_net. The container keeps the Docker-era name, dots and all, because
+# scripts/provision-site-env.sh and anything an operator types look it up that
+# way — but a name with dots is a DNS liability, so the Caddyfile proxies to the
+# dotless NetworkAlias the unit sets beside it.
+network_name: 'menu-{{ site }}'
+unit_name: '{{ network_name }}.service'
+container_name: 'menu-app.{{ host }}'
+
+# The image's own account (`node`), which keep-id maps onto podman_user.
 app_uid: 1000
 app_gid: 1000
 
-caddy_container: caddy
-caddyfile_path: /var/lib/caddy/conf/Caddyfile
+container_port: 3000
+
+# podman builds an OCI image by default and drops the Containerfile's
+# HEALTHCHECK instruction, so the unit declares the same check and the play gates
+# on it. node is in the image and the sh -c podman wraps it in handles the quotes.
+health_cmd: >-
+  node -e "fetch('http://127.0.0.1:{{ container_port }}/healthz').then(r =>
+  process.exit(r.ok ? 0 : 1)).catch(() => process.exit(1))"
+
+# ---------------------------------------------------------------------------
+# The shared Caddy unit and its Caddyfile, both owned by the caddy playbook in
+# ansible-playbooks (caddy/playbook.yml).
+# ---------------------------------------------------------------------------
+caddy_name: caddy
+caddyfile_path: '{{ podman_data_dir }}/{{ caddy_name }}/conf/Caddyfile'
 
 caddy_snippet: |
   {{ host }} {
-      reverse_proxy {{ docker_container }}:3000
+      reverse_proxy {{ network_name }}:{{ container_port }}
   }