Improve MudListItemExtended Accessibility

[PlayerModu]

Why
• Improves screen-reader/test automation behavior and overall ARIA semantics for MudListItems and associated checkboxes.

What changed
• Added a new AccessibleName property to MudListItemExtended and wired it into aria-label.
• Added role and aria-selected attributes to MudListItemExtended for correct semantics.
• Added checkbox aria-label identification

Migration notes
• No breaking changes. Consumers who want custom accessible labels can set AccessibleName on MudListItemExtended to provide an explicit aria-label.

[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 68.07%. Comparing base (28fde7e) to head (d0f06c2).
⚠️ Report is 2 commits behind head on dev.

Files with missing lines	Patch %	Lines
...mponents/ListExtended/MudListItemExtended.razor.cs	50.00%	1 Missing and 4 partials ⚠️

❌ Your patch status has failed because the patch coverage (50.00%) is below the target coverage (90.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@ Coverage Diff @@## dev #616 +/- ##
==========================================
- Coverage 68.09% 68.07% -0.03% 
==========================================
Files 107 107 Lines 7495 7504 +9 Branches 1286 1292 +6 ==========================================
+ Hits 5104 5108 +4 - Misses 1916 1917 +1 - Partials 475 479 +4 

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[mckaragoz]

Thanks 🥇