[Feature Request] Blacklist filenames for thumbnails

[nspitko]

Please describe your suggestion, and the problem it'd solve.
Thumbnails are super useful for a bunch of functionality in LRR, so it's generally important that LRR picks the right image. Unfortunately, some archives are... blessed... with a credits page, and LRR may accidentally chose that one instead of the first page or cover.

There's already a lot of logic trying to solve this, but it's a cat and mouse game as new groups show up and create their own cursed naming schemes. So instead, it might be easier to just let the user attack these en masse. usually it's a small number of groups doing this and they tend to use the same filename for all their releases, so the logic should be straightforward.

Add a text box that takes a comma separated list of filenames to ignore as cover candidates. We probably want to wildcard or ignore the extension, so something like coolgroupscans.*,overconfidentaitranslators.*. The wildcard might be overdesigning this, it could just be straight keywords, but I want to avoid a case where a group might use the cover name as part of the page name too, eg, coolscans.jpg, coolscans_p1.jpg, etc.

The ability to regenerate thumbnail on a specific archive would also be handy here for testing the rule before pulling the trigger on the whole DB, but this is more of a stretch goal.

[Asinin3]

There is already a bit of logic that tries to put gallery cover pages as the first page, and scanlator credit pages as the last page. This logic also works for thumbnail generation. See:

LANraragi/lib/LANraragi/Utils/Archive.pm

Line 250 in 9895ed7

# Move front cover pages to the start of a gallery, and miscellaneous pages such as translator credits to the end.

You could make a PR, that adds some more common names for cover images to the start, and scanlator credit pages to the end. But it is a bit unwieldy, the more you add the more likely it will break another gallery if the filenames match something which isnt a cover or credit page.

It would be nice if this setting was modifiable within LRRs settings, and had some defaults already set for common occurances only, so users can modify it themselves as its not really something that should be maintained within the main repo IMO