build(deploy): the server's checkout is ~deploy/halkyon, the repository's name

The folder kept its name from before the monorepo (ADR 0015), though
Train and Todo deploy from it too. redeploy.sh, the backup's units and
the operator's steps name ~deploy/halkyon; the Compose project keeps the
name halkyon-learn, as Docker names its volumes after it.

The server moves after this is deployed: the running redeploy.sh is read
whole before it runs, so the deploy of this commit still works in the
old folder; then the folder is moved, the pinned commands in deploy's
authorized_keys and the backup's units changed, and the containers
recreated on the new paths.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

deploy/backup/halkyon-backup.service

@@ -6,7 +6,7 @@
 # would protect little: it keeps to the basics.
 [Unit]
 Description=Off-site backup of learn.halkyon.eu's database
-Documentation=file:///home/deploy/halkyon-learn/deploy/backups.md
+Documentation=file:///home/deploy/halkyon/deploy/backups.md
 After=network-online.target docker.service
 Wants=network-online.target
 
@@ -14,7 +14,7 @@ Wants=network-online.target
 Type=oneshot
 User=deploy
 Group=deploy
-ExecStart=/home/deploy/halkyon-learn/deploy/backup.sh
+ExecStart=/home/deploy/halkyon/deploy/backup.sh
 PrivateTmp=yes
 NoNewPrivileges=yes
 ProtectSystem=full