chore: Improve Activity Library focus and hover states

[Dschoordsch]

Description

Fixes #9200

Demo

https://www.loom.com/share/8e5e9498c8594056a0b4bc0ab2b70919?sid=394eacdb-589c-4ac1-a0d4-0d5ba6134845

Testing scenarios

• focus and highlights in activity library
• create custom activity card
• create custom activity choose template screen

Final checklist

• I checked the code review guidelines
• I have added Metrics Representative as reviewer(s) if my PR invovles metrics/data/analytics related changes
• I have performed a self-review of my code, the same way I'd do it for any other team member
• I have tested all cases I listed in the testing scenarios and I haven't found any issues or regressions
• Whenever I took a non-obvious choice I added a comment explaining why I did it this way
• I added the label Skip Maintainer Review Indicating the PR only requires reviewer review and can be merged right after it's approved if the PR introduces only minor changes, does not contain any architectural changes or does not introduce any new patterns and I think one review is sufficient'
• PR title is human readable and could be used in changelog

[ackernaut]

This is looking great, Georg! I left a comment on the Loom about one small nuance for spacing below the text of the format selection sections. Not a blocker, but nice to refine.

[Dschoordsch]

I've added some more padding there.