Files under /srv/nc-files (NFS export on desslok) created at initial AIO
setup were written by uid 0 with mode 0755 root:www-data. PHP-FPM workers
run as www-data (uid 33), which can't create new files in those dirs.
Symptom: any of "Permission denied" on new document, file upload, or
Collabora discovery. Same class of bug as the Collabora
remoteData/discovery warning.
Fix: chmod g+w on the affected parents. Snapshots saved to /var/tmp
for rollback.
Add Option A (narrow target list) and Option B (sweep all
group=www-data dirs without g+w) procedures to troubleshooting.html.