feature request: Add Customization Options for Media Page Banners

[GiFuJo]

Checklist

• I checked that this feature has not been requested before
• I checked that this feature is not in the "Not planned" list
• This feature will benefit the majority of users

Problem Description / Use Case

Currently, when no banner image is provided by AniList, a cropped and zoomed version of the cover poster is used as the banner on the media page. Since AniList posters have a relatively low resolution, this often results in banners that look blurry or weird.

Proposed Solution

Introduce a setting to let users customize how banners are displayed on the media page when a dedicated banner image is not provided.

Suggested options:

• Hide the media page banner if no banner is provided.
• Show the poster as the banner when no banner is provided (current behavior).
• Always hide the media page banner, regardless of whether a banner is provided.

[Rinkerbel]

Another option that I think would be nice is to have a user provided placeholder banner when there is no banner available on Anilist.
I also think it would be cool if we could add multiple banners and have Seanime cycle through them.