Fleet UI: Fix 403, 404, 500 clouds in dark mode (#44842)

[RachelElysia]

Issue

Dark mode tweaks

Description

Merged into main with #44842
This is a cherry pick into 4.85.0

 2010  git checkout origin/rc-minor-fleet-v4.85.0
 2011  git checkout -b 404-clouds-rc
 2012  git log main
 2013  git cherry-pick a89f5dea978cfaa4cf8c60afbab2f18c4b1ba854
 2014  git push -u origin 404-clouds-rc

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 66.74%. Comparing base (9de8af6) to head (9d5c57f).
⚠️ Report is 22 commits behind head on rc-minor-fleet-v4.85.0.

Additional details and impacted files

@@                    Coverage Diff                     @@
##           rc-minor-fleet-v4.85.0   #44849      +/-   ##
==========================================================
+ Coverage                   66.72%   66.74%   +0.01%     
==========================================================
  Files                        2626     2626              
  Lines                      211198   211104      -94     
  Branches                     9428     9433       +5     
==========================================================
- Hits                       140924   140897      -27     
+ Misses                      57485    57419      -66     
+ Partials                    12789    12788       -1     

Flag	Coverage Δ
frontend	54.75% <ø> (+<0.01%)	⬆️

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[Brajim20]