web: fix scrollbar styling

[RoboMagus]

Details

Closes #11936.
This PR removes unnecessary scrollbars on the .pf-c-card__body class, as well as add scrollbar styling to browsers that do not support the ::-webkit-scrollbar. (Currently on Firefox thick unstyled grey scrollbars show up whenever a container is scrollable)

Note that this only changes the color scheme, as scrollbar thickness styling is not inherited (see this issue) and therefore would require modifying a significant number of classes to add scrollbar-width.

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Checklist

• Local tests pass (ak test authentik/)
• The code has been formatted (make lint-fix)

If an API change has been made

• The API schema has been updated (make gen-build)

If changes to the frontend have been made

• The code has been formatted (make web)

If applicable

• The documentation has been updated
• The documentation has been formatted (make website)

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.81%. Comparing base (9dddbd2) to head (4765472).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #12600      +/-   ##
==========================================
- Coverage   92.76%   91.81%   -0.95%     
==========================================
  Files         770      770              
  Lines       38873    38873              
==========================================
- Hits        36059    35690     -369     
- Misses       2814     3183     +369     

Flag	Coverage Δ
e2e	42.68% <ø> (-6.09%)	⬇️
integration	24.58% <ø> (ø)
unit	90.39% <ø> (ø)

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