[stable6] feat: cutomize file picker icon size

[backportbot]

Backport of #2580

Warning, This backport's changes differ from the original and might be incomplete ⚠️

Todo

• Review and resolve any conflicts
• Review and verify the backported changes
• Amend HEAD commit to remove the line stating to skip CI

---

Learn more about backports at https://docs.nextcloud.com/server/stable/go.php?to=developer-backports.

[susnux]

@kristian-zendato have you checked the changes contain all changes of the original PR?
If yes amend the commit and remove the [skip ci]

[codecov]

Codecov Report

❌ Patch coverage is 94.73684% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 43.98%. Comparing base (a23e95c) to head (0e80c04).
⚠️ Report is 16 commits behind head on stable6.

Files with missing lines	Patch %	Lines
lib/composables/preview.ts	94.73%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           stable6    #2601      +/-   ##
===========================================
+ Coverage    41.78%   43.98%   +2.19%     
===========================================
  Files           16       16              
  Lines          414      432      +18     
  Branches        79       86       +7     
===========================================
+ Hits           173      190      +17     
- Misses         215      216       +1     
  Partials        26       26              

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