Apply theme vars to Search page

[yurishkuro]

part of #1911

There are some visual changes to the backgrounds, but they seem for the better, stronger contrast.

Before:

After:

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.92%. Comparing base (b0040ad) to head (f1ecedd).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3180   +/-   ##
=======================================
  Coverage   97.92%   97.92%           
=======================================
  Files         260      260           
  Lines        8162     8162           
  Branches     2150     2068   -82     
=======================================
  Hits         7993     7993           
  Misses        169      169           

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