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/roles/caddy/tasks/main.yaml

@@ -1,14 +1,29 @@
 ---
+# Append this Site's block to the shared Caddyfile.
+#
+# Caddy is its own playbook (ansible-playbooks/caddy/playbook.yml) and a rootless
+# Quadlet unit there, so this role does not manage the container — it only points
+# it at the app. The Caddyfile is a bind mount into that container, so Caddy sees
+# a written change as soon as the file lands; the handler only asks Caddy to
+# re-read it. That is a reload, not a restart, so the other hosted sites are
+# untouched.
+#
+# blockinfile is idempotent on its own via the marker, so there is no need to
+# slurp the file and compare first — which also matters because slurp *fails*
+# when the Caddyfile does not exist yet, on a host where the Caddy playbook has
+# not run.
+
 - name: Check the Caddyfile exists
-  stat:
+  ansible.builtin.stat:
     path: '{{ caddyfile_path }}'
   register: menu_caddyfile
 
 - name: Fail when Caddy is not where we expect it
-  fail:
+  ansible.builtin.fail:
     msg: >-
-      {{ caddyfile_path }} is missing. Deploy the caddy playbook, which owns the
-      Caddy container and its config, before this one.
+      {{ caddyfile_path }} is missing. Deploy the Caddy playbook
+      (ansible-playbooks/caddy/playbook.yml), which owns the Caddy unit and its
+      config, before this one.
   when: not menu_caddyfile.stat.exists
 
 # The Site's web address may still be claimed by an older snippet: the retired
@@ -16,7 +31,7 @@
 # Caddy refuse the whole config, and a refused reload leaves the old proxy in
 # place, which is a 502 once the old container is gone.
 - name: Drop any older snippet claiming this web address
-  blockinfile:
+  ansible.builtin.blockinfile:
     path: '{{ caddyfile_path }}'
     marker: '# {mark} Ansible managed Caddy snippet for {{ host }}'
     state: absent
@@ -25,9 +40,12 @@
 # blockinfile replaces whatever sits between its markers, so redeploying updates
 # the snippet in place rather than appending a second one.
 - name: Point the Site's web address at the app
-  blockinfile:
+  ansible.builtin.blockinfile:
     path: '{{ caddyfile_path }}'
     marker: '# {mark} ANSIBLE MANAGED: menu app ({{ site }})'
     block: '{{ caddy_snippet }}'
-    create: no
+    create: false
+    owner: '{{ podman_user }}'
+    group: '{{ podman_user }}'
+    mode: '0644'
   notify: Reload Caddy