Move the deployment runbook out of the repository into CTXD

By owner directive (2026-10-08), all runbook information lives in the
CTXD project mealquest, file RUNBOOKS.MD, never in the repository.
Delete deploy/RUNBOOK.md, whose content is merged into that CTXD file,
and point the comments in deploy/.env.example, deploy/compose.yaml and
deploy/systemd/mealquest-media-backup.sh at RUNBOOKS.MD instead.

Maestro task e81ed994-a510-48e6-9cf6-e76d5d81f56c.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

deploy/systemd/mealquest-media-backup.sh

@@ -15,8 +15,9 @@
 # swapping the path afterwards cannot redirect it. Symlinks inside the
 # directory are copied as links (-a), never followed.
 #
-# The media directory is created at deploy time (deploy/RUNBOOK.md). If it
-# is missing the job fails; it is never treated as "nothing to back up".
+# The media directory is created at deploy time (CTXD project mealquest,
+# RUNBOOKS.MD). If it is missing the job fails; it is never treated as
+# "nothing to back up".
 #
 # rsync mirrors into .../mealquest-backups/media/ only: the target ends in
 # a slash, so --delete removes files from that directory and nothing