feat(a11y): add semantic accessibility landmarks to upload panel (#569)

[annukumar123]

#569

Core Modifications

• UploadPanel.jsx: Refactored the outer layout element container into a semantic HTML <section> bound with an aria-labelledby key mapped to an internal heading node. Wrapped error banners and success messages in an explicit role="status" aria-live="polite" active announcement region. Converted generic document item dividers into a proper screen-reader navigateable semantic list layout (<ul>/<li>).
• UploadPanel.test.jsx: Added unit assertions validating semantic region landmarks, accessibility roles, and active state tracking frameworks.

Verification Checklist

• Local accessibility validation suites executed successfully with 100% green metrics.
• Verified DOM node navigation structures behave correctly via standard layout debugging maps.

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[annukumar123]

@imDarshanGK
Both CI are working . you can verify now