laanlabs/openPlan3D ? reverse-engineered prompt

Build me a browser based floor plan editor where I can draw a home in 2D and instantly switch to a 3D walkthrough view.

I want to be able to add walls, doors, windows, stairs, rooms, text labels, and furniture by dragging things onto the plan, then move, rotate, resize, snap, and align them easily. It should feel simple enough for a non expert, but still let me do detailed work like changing room colors, applying floor and wall materials, using grid snapping, and undoing or redoing changes.

Please make it save projects locally by default, with an option to export and import the whole project, plus export to common formats like PDF, PNG, SVG, DXF, and JSON. If it makes sense, add support for bringing in an iPhone room scan and turning it into an editable plan. Keep it clean, fast, and modern, and if you need current library docs, look them up online.