Live Mode Update: Fixed 4 Step Switches + Drag Assignment

Live Mode has been redesigned for practical stage use. Instead of rendering one switch per pedal, the interface now always shows 4 step switches.

Each step switch starts as EMPTY by default. Users can assign a pedal by dragging a pedal directly from the pedalboard and dropping it onto the desired step switch.

A visual drop indicator appears on the target switch during drag to make assignment clearer and more reliable.

Clicking an assigned step switch toggles bypass for that assigned pedal only. Clicking an EMPTY switch does nothing.

Safety behavior is included: if a pedal assigned to a step is removed from the chain, that step automatically resets back to EMPTY.