Global Zoom Visibility Control for Map Layers

Current behavior:
Zoom visibility must be adjusted per layer. When multiple layers are present, changing the visibility range requires moving each slider individually. This is inefficient when applying the same zoom range across all layers (e.g., reducing detail at wider scales).

Proposal:
Add a master/global zoom visibility control at the top of the layer list.

• Adjusting the master control sets the same min/max zoom range for all layers.

• Users can optionally override individual layers afterward.

Benefits:

• Significant time reduction when configuring many layers.

• Consistent map behavior when applying high-level visibility rules.

• Improves usability without changing existing functionality.

Scope:
This is an additive UI enhancement—no impact on current workflows, scripting, or backward compatibility.