planka: migrate data paths to new v2 directory structure

Planka v2.0.1 moved all uploads to a unified data directory:
- public/{favicons,user-avatars,background-images} -> data/protected/
- private/attachments -> data/private/

The update script was still restoring files to the old locations,
which made attachments, avatars and backgrounds disappear after
updating from rc.4 to 2.0.1.

Changes:
- update_script: backup handles both old and new layouts
- update_script: restore now uses new v2 paths
- install script: create v2 data directories on fresh install

Ref #12066

install/planka-install.sh

@@ -50,6 +50,7 @@ cp .env.sample .env
 sed -i "s#http://localhost:1337#http://$LOCAL_IP:1337#g" /opt/planka/.env
 sed -i "s#postgres@localhost#planka:$DB_PASS@localhost#g" /opt/planka/.env
 sed -i "s#notsecretkey#$SECRET_KEY#g" /opt/planka/.env
+mkdir -p /opt/planka/data/protected/{favicons,user-avatars,background-images} /opt/planka/data/private/attachments
 $STD npm run db:init
 msg_ok "Configured PLANKA"