Color Scheme Customization

[zulqarnainhanif]

Summary

• Allow creating a light/dark mode theme in Admin Panel Settings
• Save custom settings in DB table

References

closes #5755

Checklist

• CI/CD checks pass npm run check
  • Linter passing via npm run lint
  • Typescript passing via npm run check-errors
  • Unit & Integration tests passing via npm run test
  • Docker build process passing via npm run build-client
• If this PR is still a WIP, convert to a draft
• When this PR is ready, mark it as "Ready for review"
• Changes have been manually QA'd
• Changes reviewed by at least 2 approved reviewers

Reviewers

@HexaField