fix: text-only mode leaves speaker and camera-flip controls visible

[swsarancodes]

Reproduction

1. Start GitAgent without a configured voice API key.
2. Open the local UI.

Actual

The text-only warning appears and Camera, Mic, and Screen are hidden, but the camera-flip and Speaker controls remain visible. The Speaker control is missed because the UI does not have the .speaker-toggle selector the handler targets.

Expected

When voice mode is unavailable, every voice-only control should be hidden; text chat remains available.