🐛(frontend) handle missing device errors gracefully

Handle the "requested device not found" error surfaced in production
when users arrive without a microphone or camera available on their
computer. Some devices also have a hardware button that physically
locks the microphone and makes it invisible to the browser.

Instead of failing loudly, surface a clearer state to the user so
they can still proceed with whatever device is actually available.

src/frontend/src/features/analytics/telemetry.ts

@@ -133,7 +133,8 @@ export const captureMediaEvent = async (
     | 'media-device-error'
     | 'media-acquisition'
     | 'media-device-topology'
-    | 'media-device-success',
+    | 'media-device-success'
+    | 'device-not-found',
   props: Record<string, unknown>
 ) => {
   captureEvent(event, { ...props, ...(await deviceSnapshot()) })