feat(theming): Increase blur radius

[kra-mo]

Summary

25px is a bit small for large surfaces

Also discussed with @jancborchardt

Before	After

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)
• Labels added where applicable (ex: bug/enhancement, 3. to review, feature component)
• Milestone added for target branch/version (ex: 32.x for stable32)

AI (if applicable)

• The content of this PR was partly or fully generated using AI

[susnux]

Have you checked this with different devices? IIRC the value was chosen because Chrome otherwise is overloaded (extreme GPU usage).

[kra-mo]

Yeah, that was my concern as well. I mean, I have a MacBook, so I can't exactly simulate a crappy computer easily. But I would have also assumed that browsers would do a better job at optimizing this stuff by now, there are a lot of really efficient blur algos.