Cut the comment bloat from the Podman playbooks

Comment blocks now stay within three lines and explain only the non-obvious. Long histories, include examples, and commented-out code are gone. No task, key, or value changed; the only data change is comment text inside the generated unit files.

nextcloud/roles/valkey/handlers/main.yaml

@@ -1,18 +1,6 @@
 ---
-# Valkey is its own playbook (valkey/playbook.yml) and a rootless Quadlet unit
-# there. This handler runs as the connection user, which is what makes
-# `systemctl --user` work here.
-#
-# Required by valkey/roles/attach, which notifies it whenever this app's drop-in
-# changes: a new drop-in changes the generated unit, so Valkey must be recreated
-# to join the network — Quadlet has no live equivalent of
-# `podman network connect`.
-#
-# Data survives the recreate: RDB persistence is on by default, the stop is
-# graceful, and the new container loads the snapshot back off the bind mount. What
-# does not survive is availability — for the seconds the container is down,
-# Nextcloud's PHP sessions and `memcache.locking` are unreachable. See
-# valkey/readme.md, "The trade-off".
+# A new drop-in changes the generated unit, so Valkey is recreated to join the network.
+# Data survives the recreate, but Nextcloud's cache and locks are unavailable for the seconds it is down.
 - name: Restart Valkey
   ansible.builtin.systemd_service:
     name: "{{ valkey_unit }}"