Make remote voice audio playback explicit

[JulioMCruz]

What changed

• attach remote LiveKit audio to an explicit unmuted HTML audio element
• enable autoplay and inline playback, hide controls, and call play() directly
• expose only safe connected/playing/browser-permission status in the voice card
• detach, pause, and remove remote audio on unsubscribe, failure, end, or unmount
• add focused playback and cleanup regression tests

Why

Implicitly appending LiveKit's generated element did not make playback success or browser autoplay rejection observable and made lifecycle cleanup harder to prove.

Validation

• typecheck and ESLint passed
• 2 focused suites / 6 tests passed
• production build generated all 51 routes with non-secret placeholder Firebase values
• diff and secret scans passed

No real call, audio capture, credential operation, or deployment occurred.