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

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[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   +/-   ##
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  Coverage    76.64%   76.64%           
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  Files          169      169           
  Lines        13836    13836           
========================================
  Hits         10605    10605           
  Misses        3231     3231           

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

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[yyassi-heartex]

/git merge develop

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

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[yyassi-heartex]

/git merge develop

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