Speakers stay muted after double-tap lock recording (mute audio behavior)

**Describe the bug**
When the audio behavior is set to "Mute" in settings, using double-tap lock to record leaves the system volume at 0 after transcription completes. Speakers stay muted until you manually adjust the volume.

This does not happen with regular press-and-hold recording — only with the double-tap lock flow.

**To Reproduce**
1. Go to Settings → set audio behavior to "Mute"
2. Play some audio so you can hear the speakers
3. Double-tap the hotkey quickly to enter lock mode
4. Say something
5. Tap the hotkey once to stop and transcribe
6. Speakers remain muted after transcription finishes

**Expected behavior**
System volume should be restored to its original level once transcription is complete, the same way it works with press-and-hold.

**Desktop**
- Version: 0.7.5

Start by comparing the double-tap lock recording flow with the press-and-hold flow, focusing on audio mute and volume restoration after transcription completes. Done means the original system volume is restored after stopping a locked recording while the audio behavior is set to Mute.

Written by the indexing model from the issue text.