[fank]

Summary

• Use exec-style setpriv instead of runuser so slow saves can finish within Docker’s configured stop timeout.
• Preserve SAVE_NAME on first startup and consistently resolve it on restart.
• Avoid conflicting --port arguments when BIND already includes a port.
• Apply DLC settings during scenario conversion and use the selected mod directory across scenario entrypoints.

Closes #599.
Closes #603.
Closes #455.
Closes #588.

Validation

• All 21 existing regression methods pass; ShellCheck and whitespace checks pass.
• Runtime changes are unchanged from the previously tested images: regular/rootless startup, save reuse, BIND, RCON and clean shutdown passed.
• The prior shutdown reproduction showed the baseline interrupting a five-second save after 2.10s; the fixed image completed it in 5.20s.
• Removed the two added Python test files following maintainer feedback. Kept the small adjustment to the existing configuration-path test.