Use Custom Theme from DB in Client

[zulqarnainhanif]

Summary

• Replace old variable with custom theme variables throughout app
• On saving new theme change the theme on run-time
• Fix Sketch Color Picker when selected near screen end
• Refactor ClientTheme.jsx Code
• Add Stuff in Demo Area in Client Theme maker
  • Table (used in admin panels)
  • Dropdown hover Background
  • Popup Background
  • Editor dock panel Background

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 @speigg

[speigg]

Something wrong with header colors in the Theme "Demo Area", but otherwise looks great!

[speigg]

A few other minor suggestions:

• Can we rename "Demo Area" to Theme Playground"
• A button to reset to the default theme

[zulqarnainhanif]

A few other minor suggestions:

• Can we rename "Demo Area" to Theme Playground"
• A button to reset to the default theme

have added both the changes @speigg