Themes/Tweaks browser, sharing/import, custom themes/tweaks, and repo

[7w1]

Description

Still a WIP, I'll update this PR description with more details later.

Pulls themes and tweaks from https://github.com/SableClient/themes and allows basic searching and filtering in the themes settings
Theme links that end in *.preview.sable.css from the official repo will generate embeds, optional setting to allow generating embeds for any *.preview.sable.css file.
In chat previews are generated with extracted css values and are safe from injection. Full theme files will load the entire file, and are vulnerable to injection, hence the official safe repo. Third party themes sent in chat show a prominent banner making the risks clear

Mitigates #492 ?
Fixes #71
Fixes #617 (via tweak in theme repo)

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change - disables themes, but there's a migration modal that prompts the user with 1 click to redownload and enable their existing theme(s).
• This change requires a documentation update

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings

AI disclosure:

• Partially AI assisted (clarify which code was AI assisted and briefly explain what it does).
• Fully AI generated (explain what all the generated code does in moderate detail).

AI was used to write the code for parsing and extracting data from the raw css files/links and dynamically populate the lists as well as develop the migration system for current themes. Tests were AI generated.
All code has (or will be) thoroughly reviewed by me by the time this PR is ready.

[Septicity]

I figure that proper custom CSS theming will require more thorough CSS-visible class names for each component; is that part of the plans for this, or would that be better accomplished with a tracking issue for another time?

[7w1]

I figure that proper custom CSS theming will require more thorough CSS-visible class names for each component; is that part of the plans for this, or would that be better accomplished with a tracking issue for another time?

I think that's better as a separate issue.

[github-actions]

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[github-actions]

Deploying with    Cloudflare Workers

Status	Preview URL	Commit	Alias	Updated (UTC)
✅ Deployment successful!	https://pr-633-sable.raspy-dream-bb1d.workers.dev	4b17220	pr-633	Sat, 04 Apr 2026 07:35:53 GMT