feat: OPTIC-1217: Implement Color design tokens as CSS variables and Dark Mode

[yyassi-heartex]

PR fulfills these requirements

• Commit message(s) and PR title follows the format [fix|feat|ci|chore|doc]: TICKET-ID: Short description of change made ex. fix: DEV-XXXX: Removed inconsistent code usage causing intermittent errors
• Tests for the changes have been added/updated (for bug fixes/features)
• Docs have been added/updated (for bug fixes/features)
• Best efforts were made to ensure docs/code are concise and coherent (checked for spelling/grammatical errors, commented out code, debug logs etc.)
• Self-reviewed and ran all changes on a local instance (for bug fixes/features)

Change has impacts in these area(s)

(check all that apply)

• Product design
• Backend (Database)
• Backend (API)
• Frontend

Describe the reason for change

significant improvement to ui tokens + adding the ability to toggle between Auto, Light and Dark mode

[netlify]

✅ Deploy Preview for heartex-docs canceled.

Name	Link
🔨 Latest commit	cb15ba7
🔍 Latest deploy log	https://app.netlify.com/sites/heartex-docs/deploys/6748d1b893daf50008b00006

[netlify]

✅ Deploy Preview for label-studio-docs-new-theme canceled.

Name	Link
🔨 Latest commit	cb15ba7
🔍 Latest deploy log	https://app.netlify.com/sites/label-studio-docs-new-theme/deploys/6748d1b8d6714e00084b2d2a

[robot-ci-heartex]

Follow Merge downstream workflow has been failed.

Workflow run

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 76.64%. Comparing base (407e456) to head (b90d3b9).
Report is 2 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #6550   +/-   ##
========================================
  Coverage    76.64%   76.64%           
========================================
  Files          169      169           
  Lines        13836    13836           
========================================
  Hits         10605    10605           
  Misses        3231     3231           

Flag	Coverage Δ
pytests	76.64% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[yyassi-heartex]

/git merge develop

Workflow run
Successfully merged: 7 files changed, 13 insertions(+), 13 deletions(-)

[robot-ci-heartex]

Follow Merge downstream workflow has been failed.

Workflow run

[robot-ci-heartex]

Follow Merge downstream workflow has been failed.

Workflow run

[robot-ci-heartex]

Follow Merge downstream workflow has been failed.

Workflow run

[yyassi-heartex]

/git merge develop

Workflow run
Successfully merged: create mode 100644 web/apps/labelstudio/src/pages/DataManager/api-config.example.js