TuneUp Version 27 validation

Number-row station design:
- 1 selects Main.
- 2,3,4,5,6,7,8,9,0 select the first nine saved playlists in station order.
- Additional playlists remain available through F2.
- Number keys no longer select individual songs.

Main station:
- Starts empty on each TuneUp launch.
- Old persistent Main playlist files are removed at startup.
- Music opened from Windows, O, or computer scan is loaded into Main for the current session.
- Main does not auto-advance when a song finishes.

Saved playlists:
- Remain persistent.
- Continue automatically to the next song when playback finishes.

Arrange Stations:
- Available under F2 Playlist Manager.
- User selects a playlist in a native Windows list.
- A second native dialog provides Move Up and Move Down buttons reachable with Tab.
- Order is stored in station-order.txt in the TuneUp application-data folder.

Build validation:
- Windows amd64 test binary compiled with go test -c.
- Windows amd64 TuneUp.exe compiled successfully.
