Add session storage keys for branding assets caching

[olexii4]

What does this PR do?

This PR fixes the branding logo loader performance issue by adding session storage caching for logo path and favicon. Previously, the loader made multiple 404 HTTP requests sequentially on every page load while detecting the correct image format, and the favicon update was delayed until the cluster config API responded.

Key Changes:

1. Session Storage Caching - Added local constants branding-logo-path and branding-favicon in brandingLoader.ts for caching branding assets between page loads using direct window.sessionStorage access

2. Parallel Logo Format Detection - All image formats (jpg, jpeg, png, gif, webp, svg) are checked in parallel using Promise.all. The first successful format (by priority order) is cached immediately

3. Placeholder Favicon in HTML - Changed index.html to use a 1x1 transparent GIF placeholder instead of referencing favicon.ico. Removed the id attribute, now using link[rel="shortcut icon"] selector

4. Favicon Preload Caching - Favicon is loaded from session storage cache immediately during the preload phase (in brandingLoader.ts) before React bootstrap starts

5. updateFavicon Function - Exported from brandingLoader.ts, accepts DashboardFavicon | undefined:

   • If dashboardFavicon is provided, uses its base64data and mediatype
   • If undefined, fetches /dashboard/assets/branding/favicon.ico and converts to data URL
   • Caches the result in session storage and updates the DOM

6. checkFavicon Method - Simplified in bootstrap/index.ts to call the imported updateFavicon function with the dashboard favicon from Redux state

Screenshot/screencast of this PR

What issues does this PR fix or reference?

fixes eclipse-che/che#23690

Is it tested? How?

Release Notes

Docs PR

[che-bot]

Click here to review and test in web IDE:

[github-actions]

Docker image build succeeded: quay.io/eclipse/che-dashboard:pr-1438

kubectl patch command

kubectl patch -n eclipse-che "checluster/eclipse-che" --type=json -p="[{"op": "replace", "path": "/spec/components/dashboard/deployment", "value": {containers: [{image: "quay.io/eclipse/che-dashboard:pr-1438", name: che-dashboard}]}}]"

[github-actions]

Docker image build succeeded: quay.io/eclipse/che-dashboard:pr-1438

kubectl patch command

kubectl patch -n eclipse-che "checluster/eclipse-che" --type=json -p="[{"op": "replace", "path": "/spec/components/dashboard/deployment", "value": {containers: [{image: "quay.io/eclipse/che-dashboard:pr-1438", name: che-dashboard}]}}]"

[codecov]

Codecov Report

❌ Patch coverage is 94.57831% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 92.79%. Comparing base (e8f3c6f) to head (eb074d0).
⚠️ Report is 11 commits behind head on main.

Files with missing lines	Patch %	Lines
...s/dashboard-frontend/src/preload/brandingLoader.ts	94.23%	9 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1438      +/-   ##
==========================================
+ Coverage   92.59%   92.79%   +0.19%     
==========================================
  Files         520      520              
  Lines       48819    48943     +124     
  Branches     3621     3645      +24     
==========================================
+ Hits        45206    45415     +209     
+ Misses       3575     3490      -85     
  Partials       38       38              

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[svor]

LGTM

[openshift-ci]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: olexii4, svor

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