[Improved, Fixed] Mic permission hotfix

Improvements

• The web-interview button now verifies microphone access before connecting, so candidates get instant feedback if their mic is blocked.

Fixes

• Fixed a bug that let calls start reserving a line even when the candidate’s microphone wasn’t available, which often ended in a generic error after a delay. Calls now fail fast with a clear mic-denied or mic-unavailable message and no longer eat into voice-interview capacity.