feat: read system default theme.

[35C4n0r]

Closes #2592

📑 Description

✅ Checks

• My pull request adheres to the code style of this project
• My code requires changes to the documentation
• I have updated the documentation as required
• All the tests have passed

ℹ Additional Information

[vercel]

@35C4n0r is attempting to deploy a commit to the KeepHQ Team on Vercel.

A member of the Team first needs to authorize it.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 31.10%. Comparing base (892a79e) to head (b1cd5ee).
Report is 41 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #2651       +/-   ##
===========================================
- Coverage   69.63%   31.10%   -38.54%     
===========================================
  Files         160       64       -96     
  Lines       15149     7015     -8134     
===========================================
- Hits        10549     2182     -8367     
- Misses       4600     4833      +233     

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