fix(ui): improve screen reader feedback for code snippet copy action

[Tugamer89]

What: Replaced the dynamic inline aria-live state change on the code block copy button with a dedicated, visually hidden aria-live region (sr-announcer) that reliably announces "Code copied to clipboard".

Why: Modifying the aria-label or contents of an element that already has focus and an inline aria-live attribute is famously unreliable across screen readers. A dedicated, off-screen live region is the standard pattern for programmatic UI announcements.

Before/After: Visually identical. A screenshot of the "Copied!" state was provided via Playwright execution.

Accessibility: Greatly improves screen reader reliability by properly announcing asynchronous state changes using the standard aria-live="polite" and aria-atomic="true" techniques.

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PR created automatically by Jules for task 1302221385556577449 started by @Tugamer89

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud