Add background styling to user profile cards

[nushea]

Description

Add user styling to the background of user cards. This follows commet's background styling for interoperability.

This could use a logarithmic shading but that would imply either adding a new external library or doing some math that could be too complex for the purposes of this.

(ideal example)

(normal example)

(anti-ideal example)

(normal example)

(look of the new setting)

(look of it when it is light)

Type of change

• New feature (non-breaking change which adds functionality)

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
• 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).

Made with the weird feeling of not knowing what to do with my life anymore <3