fix: use correct boundaries of CSS breakpoints

[susnux]

☑️ Resolves

We mixed up breakpoints in the source code, sometimes mobile is max-width 1024, and sometimes width < 1024.
Meaning sometimes mobile is <= 1024 sometimes < 1024.

This now is consistent mobile: width < 1024.

Follow-up on nextcloud/server#57010

🏁 Checklist

• ⛑️ Tests are included or are not applicable
• 📘 Component documentation has been extended, updated or is not applicable
• 2️⃣ Backport to stable8 for maintained Vue 2 version or not applicable

[susnux]

/backport to stable8

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 54.60%. Comparing base (183d635) to head (aa51f0d).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #8520   +/-   ##
=======================================
  Coverage   54.60%   54.60%           
=======================================
  Files         106      106           
  Lines        3443     3443           
  Branches     1005     1004    -1     
=======================================
  Hits         1880     1880           
  Misses       1322     1322           
  Partials      241      241           

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