Redesign index pages

[philippjfr]

Aligns the index page design with the error page changes in #6496.

Overall I'm aiming for a cleaner and more neutral look for the default pages. The previous version was really nice particularly with the theme toggle etc. but pulling in a whole design toolkit for a simple static page seemed like a lot and with the banner it felt quite busy.

Compared to the old version:

[ahuang11]

Do app previews support descriptions, or just name?

Also, would it make sense to swap the location of search and Running 7 applications?

[philippjfr]

Do app previews support descriptions, or just name?

To be precise they support neither, these are simply the app filenames after being transformed with name.replace("_", " ").title()

Also, would it make sense to swap the location of search and Running 7 applications?

Think I prefer this.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.02%. Comparing base (aea6cdf) to head (fe7990f).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6497      +/-   ##
==========================================
- Coverage   82.08%   82.02%   -0.06%     
==========================================
  Files         314      314              
  Lines       46358    46358              
==========================================
- Hits        38052    38026      -26     
- Misses       8306     8332      +26     

Flag	Coverage Δ
ui-tests	36.44% <ø> (-0.23%)	⬇️
unitexamples-tests	71.44% <ø> (+0.01%)	⬆️

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