Implement Mobile Action Bar for Camera and Mic

[bryanngongeh]

Create a new BottomActions.tsx component to provide a bold, persistent action bar on mobile for quick Start/Stop camera/mic and persona toggle. This should be rendered in App.tsx for widths less than 768px.

• Acceptance Criteria:

• A persistent action bar is visible at the bottom of the screen on mobile devices.

• The action bar includes buttons for camera Start/Stop and mic Start/Stop.

• A persona toggle is present in the action bar.

• The action bar is responsive and functions correctly across different mobile orientations.