Floorplan UI: topology overlays and radio intensity layer

[DarinShapiro]

Summary

Implement the visual front-end for spatial diagnostics on top of floorplan graphics.

Why

A physical view is the most intuitive way for operators to understand network deployment and troubleshoot RF issues.

Scope

• Overlay Rendering: Project nodes and links onto the floorplan SVG/canvas.
• Heatmap Toggle: UI control to switch between topology-only and RF intensity heatmap views.
• Interaction: Support zoom, pan, and node inspection within the spatial context.
• Fallback UI: Cleanly switch to an 'Area Graph' view when a full floorplan is not configured.

Acceptance Criteria

• Nodes and links are correctly positioned over floorplan elements.
• Heatmap layer clearly highlights high-stress or low-signal zones.
• Performance remains responsive even with complex floorplans.