Add `aria-live` Region for Toast Notifications

[Emmzyemms]

Description:
ToastProvider and RateLimitToast display transient notifications. Screen readers won't announce these because there's no aria-live region. Users relying on assistive technology won't know when rate limiting, errors, or success messages appear.

Acceptance Criteria:

• The toast container element has aria-live="polite" (or "assertive" for errors)
• Each toast has role="status" for non-urgent messages or role="alert" for errors
• Toast auto-dismiss timing is sufficient for screen reader users (minimum 5 seconds)
• Verified with NVDA/VoiceOver that toasts are announced

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[AvatarMiiDe]

@AvatarMiiDe has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

can i please handle these

ℹ️ Repo Maintainers: To accept this application, review their application or assign @AvatarMiiDe to this issue.

[drips-wave]

Congratulations, @AvatarMiiDe! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 30, 2026.

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