Fixes#1583
The fixPermissions function in file manager was causing sites to become
inaccessible after running "Fix Permissions" on Ubuntu 24. The root causes:
1. Async execution (popenExecutioner) caused race conditions where commands
executed in unpredictable order
2. The public_html directory group was incorrectly changed from 'nogroup'
to the user's group, breaking web server access
Changes:
- Changed all async popenExecutioner calls to sync executioner calls
- Reordered commands to set permissions before ownership
- Ensured public_html directory maintains correct group ownership (nogroup)
- Added comments to clarify the purpose of each step
This ensures the file manager's "Fix Permissions" feature works correctly
on Ubuntu 24 while maintaining proper security.
