fix: guard getUserMedia call against undefined mediaDevices in non-secure contexts

[tomasmach]

Summary

• Adds a guard check for navigator.mediaDevices and navigator.mediaDevices.getUserMedia before attempting to access the microphone in AudioSampleRecording.tsx
• Prevents a crash (Cannot read properties of undefined (reading 'getUserMedia')) that occurs in non-secure (HTTP) contexts where navigator.mediaDevices is undefined
• The error surfaced when closing the voice profile edit screen in remote/non-HTTPS setups (e.g. Windows desktop app pointing at a remote server)

Root cause

navigator.mediaDevices is only available in secure contexts (HTTPS or localhost). On plain HTTP, it is undefined. The cleanup effect unconditionally called .getUserMedia(...) on mount, causing an unhandled exception when the component unmounted — even if the user never interacted with the record tab.

Fix

  useEffect(() => {
    if (!showWaveform) return;
+   if (!navigator.mediaDevices || !navigator.mediaDevices.getUserMedia) return;

Credit

Bug found and fix identified by AuroraSkye on the Voicebox Discord. Thank you!