Fix contrast accessibility bugs

[ReneOv-MSFT]

Fixes issues with contrasting colors:

• Darker focus box when using keyboard controls in tab selection.
• Darker text when surrounding text links for clearer contrast.

https://azurebatch.visualstudio.com/BatchExplorer/_workitems/edit/1124
https://azurebatch.visualstudio.com/BatchExplorer/_workitems/edit/1125
https://azurebatch.visualstudio.com/BatchExplorer/_workitems/edit/1135
https://azurebatch.visualstudio.com/BatchExplorer/_workitems/edit/1128

[codecov]

Codecov Report

Merging #2830 (2d2f3f1) into main (8b49582) will not change coverage.
The diff coverage is n/a.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2830   +/-   ##
=======================================
  Coverage   67.29%   67.29%           
=======================================
  Files        1228     1228           
  Lines       33604    33604           
  Branches     6205     6205           
=======================================
  Hits        22615    22615           
  Misses      10842    10842           
  Partials      147      147           

Files	Coverage Δ
desktop/src/@batch-flask/ui/tabs/tab.component.ts	100.00% <ø> (ø)

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