Added the ability to set custom names and box art for games

[Samuel-N-Tester]

Added the ability to set games with a custom name and a custom image perfect for ROM hacks where they have no official artwork.

The names often have version numbers that you want to keep on the file but may want to trim the version numbers out of the name shown in this app.

Before	After

How the changes work

There are two new options:

• Add custom name
• Add custom artwork

If the ROM already has a custom name or artwork then these will be replaced with Remove variants of the buttons

New menu items	Prefilled name changer	new menu items are changed to remove variants

Related Issues

#36
#209
#609

[Samuel-N-Tester]

Found a bug, fixing before review—please hold off for now.

Switching to storing a copy of the image as if its external I wont have persistent permission to read it.

[Samuel-N-Tester]

Fix by copying the selected image into the app's own external files
directory (custom-covers/cover_.) instead of storing the
picker URI directly. The file extension is resolved from the source
MIME type so all image formats are preserved correctly. Also clean up
cover files when a ROM is removed during library rescan to avoid
orphaned files accumulating.