ci: ECHO-413: Remove LSO Server Dependency from E2E Workflow

[luarmr]

🎯 Purpose
Remove unnecessary LSO server dependency from the yarn e2e workflow to simplify CI pipeline and reduce potential failure points.

📋 Changes
❌ Removed "Run LSO server" step that starts Docker container
❌ Removed corresponding "Kill LSO server" cleanup step
✅ Maintained all frontend e2e testing capabilities
✅ Reduced workflow complexity and execution time

🔍 Background
The e2e workflow was starting a full Label Studio backend server via Docker, but the frontend e2e tests don't actually require backend connectivity. This was adding unnecessary complexity, Docker dependencies, and potential failure points to our CI pipeline.

✅ Testing
[x] Verified workflow runs successfully with act - current pr too
[x] Confirmed frontend e2e tests pass without backend server
[x] Validated no tests depend on LSO server endpoints
[x] Checked workflow execution time improvement

[netlify]

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

Name	Link
🔨 Latest commit	3eb6493
🔍 Latest deploy log	https://app.netlify.com/projects/label-studio-docs-new-theme/deploys/68cdde0d0a74f20008c19ed5

[netlify]

✅ Deploy Preview for label-studio-storybook canceled.

Name	Link
🔨 Latest commit	3eb6493
🔍 Latest deploy log	https://app.netlify.com/projects/label-studio-storybook/deploys/68cdde0da555950008d19858

[netlify]

✅ Deploy Preview for label-studio-playground canceled.

Name	Link
🔨 Latest commit	3eb6493
🔍 Latest deploy log	https://app.netlify.com/projects/label-studio-playground/deploys/68cdde0da4b2cd000813640f

[netlify]

✅ Deploy Preview for heartex-docs canceled.

Name	Link
🔨 Latest commit	3eb6493
🔍 Latest deploy log	https://app.netlify.com/projects/heartex-docs/deploys/68cdde0da4b2cd000813640b

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 60.53%. Comparing base (c9a270d) to head (3eb6493).
⚠️ Report is 3 commits behind head on develop.

❗ There is a different number of reports uploaded between BASE (c9a270d) and HEAD (3eb6493). Click for more details.

HEAD has 1 upload less than BASE

Flag	BASE (c9a270d)	HEAD (3eb6493)
pytests	1	0

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #8485      +/-   ##
===========================================
- Coverage    67.34%   60.53%   -6.82%     
===========================================
  Files          780      543     -237     
  Lines        59523    38427   -21096     
  Branches     10142    10142              
===========================================
- Hits         40087    23260   -16827     
+ Misses       19433    15164    -4269     
  Partials         3        3              

Flag	Coverage Δ
lsf-e2e	54.68% <ø> (+0.01%)	⬆️
lsf-integration	51.30% <ø> (+0.02%)	⬆️
lsf-unit	8.60% <ø> (ø)
pytests	?

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.

🚀 New features to boost your workflow:

• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.