APM Planner.ini.lock - lockfile can make APM Planner stop working

if "APM Planner.ini.lock" for some reason is left (like after a crash/shutdown)
- then APM planner will be stuck at splashcreen "forever" - until the file is deleted.

maybe display a hint about it, or better - ask for ok to delete the file.

Start by locating the startup path that handles "APM Planner.ini.lock" and leads to the splash screen. Reproduce the stuck state with a leftover lockfile, then determine whether completion means showing a hint or requesting confirmation before deleting it.

Written by the indexing model from the issue text.