This patch fixes CSV imports on systems such as AlmaLinux where MariaDB's `PrivateTmp` setting hides Webmin's temporary files.
The earlier permissions fix could not solve this because the database service still could not see the file.
Imports now use a unique directory under `secure_file_priv`, or the database's data directory, while retaining restricted file permissions and automatic cleanup.
The directory uses the `#sql-` prefix so MariaDB does not treat it as a database during listings, backups, or checks.
Verified live on Debian 13, AlmaLinux 10, Ubuntu 26.04 MariaDB and MySQL 8.4, including database listings and full dumps taken while an import is in progress.
This patch fixes MySQL imports that fail because the database server cannot read the temporary file.
Since the temporary copy is created with mode 0600, a server-side `mysqlimport` fails for imports from a local file, and for uploads by users with a Unix user restriction.
Before running the import as root against a local server, the file is now given the group of the running server process with mode 0640, so the server can read it while other users still cannot. The process is found through the server's reported PID file and must be `mysqld` or `mariadbd`; otherwise the permissions are left unchanged.
ⓘ Centralize global file ACL checks for server-local reads and applies them to batch, LDAP batch, MySQL, and PostgreSQL local import and restore flows. Files are read under the configured `fileunix` identity and staged with the correct command-user ownership, preventing constrained Webmin users from bypassing `root`, `otherdirs`, or `fileunix`.
9ceffce70f (r191495975)
