feat(deploy): nightly backup script (mongodump + minio volume, 14-day rotation)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

deploy/stc/README-STC.md

@@ -45,7 +45,7 @@ Nightly cron on the VPS (`/etc/cron.d/tailchat-backup`) dumps MongoDB and tars t
 MinIO volume into `/root/backups/tailchat/`, keeping 14 days.
 
 Restore: stop the stack, `mongorestore` the dump into the `mongo` container, untar the
-MinIO volume back into `tailchat-server_storage`, start the stack.
+MinIO volume back into `tailchat_storage`, start the stack.
 
 ## Ports exposed publicly
 

deploy/stc/backup.sh

@@ -0,0 +1,18 @@
+#!/bin/sh
+# Nightly Tailchat backup: mongodump + MinIO volume tar, 14-day rotation.
+# Installed at /opt/tailchat/backup.sh, run by /etc/cron.d/tailchat-backup.
+set -eu
+
+TS=$(date +%Y%m%d)
+DEST="/root/backups/tailchat/$TS"
+mkdir -p "$DEST"
+
+cd /opt/tailchat
+docker compose exec -T mongo mongodump --archive --gzip --db tailchat > "$DEST/mongo-tailchat.archive.gz"
+docker run --rm -v tailchat_storage:/data:ro -v "$DEST":/backup alpine \
+  tar czf /backup/minio-storage.tar.gz -C /data .
+
+# rotate: drop day-dirs older than 14 days
+find /root/backups/tailchat -maxdepth 1 -mindepth 1 -type d -mtime +14 -exec rm -rf {} +
+
+echo "$(date -Is) backup ok: $(du -sh "$DEST" | cut -f1)"