ansible: nightly restic backups to both object storage regions

Hetzner's server backups cost 20% of each server's price and only
restore whole disks. Back up what matters with restic instead, into the
backup buckets we already pay for: one repository per host in hel1
(asxpio-backups-main) and one in fsn1 (asxpio-backups-repl), written
independently so either region alone is a full copy.

Postgres goes in as a dump, Forgejo's and vhpbot's SQLite databases
through the online backup API, Garage with a fresh metadata snapshot,
ejabberd through its own backup command. Keeps 7 daily, 4 weekly and
6 monthly snapshots, prunes on Sundays, and mails the journal when a
run fails.

restic is the pinned upstream release, so its version is tracked in
the repo like everything else. The vault gains the restic password
and the Xray config for the role that follows.

Assisted-by: Claude:opus-5-5

ansible/site.yaml

@@ -36,6 +36,12 @@
   roles:
     - { role: forgejo, tags: [forgejo] }
 
+- name: Backups
+  hosts: asxpio
+  become: true
+  roles:
+    - { role: restic_backup, tags: [restic] }
+
 # Last: when the pipeline changes the runner it recreates the container
 # that is running the pipeline. Everything else is done by then; that job
 # ends as failed and the next run confirms the result.