🐛(telemetry) tag in-room permission failures with their own path

Since `ToggleDevice` renders on both the join screen and in the
room, `requestDevicePermission` was reporting in-room denials
through the join-preview handler, inflating the `join_preview_failure`
funnel.

Rename `onJoinPreviewError` to `onMediaPermissionError` and thread
a `path` parameter through, derived from `ToggleDevice`'s existing
`context` prop. In-room failures are now reported under a new
`room_media_failure` code, keeping `join_preview_failure` intact
for existing dashboards.

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

@@ -19,6 +19,7 @@ export const captureEvent = (
 export type LogCode =
   // media
   | 'join_preview_failure'
+  | 'room_media_failure'
   | 'livekit_room_error'
   | 'device_switch_failure'
   | 'permission_poll_failure'