Error messages and NetworkBanner missing aria-live regions

[k-deejah]

Problem

ConnectScreen.tsx and TopBar.tsx render error messages in a p tag without role="alert". When an error occurs, screen readers will not announce the new content because there is no live region declared.

NetworkBanner.tsx renders a colored banner that changes on network switch, but has no role="status" or aria-live attribute, so the change goes unannounced.

Solution

Add role="alert" to error paragraphs in ConnectScreen.tsx and TopBar.tsx. Add role="status" and aria-live="polite" to the NetworkBanner container.

Acceptance Criteria

• Error paragraph in ConnectScreen.tsx has role="alert"
• Error banner in TopBar.tsx has role="alert"
• NetworkBanner.tsx has role="status" and aria-live="polite"
• Screen readers announce errors immediately when they appear
• Network banner changes are announced politely

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Note for Contributors: If you are assigned to this issue, write a clear and detailed description for your pull request. Explain what was changed, why it was needed, how it was implemented, and include any relevant testing or screenshots where applicable.