v0.13.0-beta.1

Added

• Snap menu while tracing (#36). Choose what new points snap onto: everything, only shapes of the kind you're drawing (so a wall traced along a room's edge stays where you put it), or nothing. Remembered per browser; Shift still frees a single point.
• Property tab scale (#6). Once a placed building has a floor with Set Scale done, the Property tab works out its own scale from it. Shown top-right, with a warning if placed buildings disagree. Outdoor devices now get real-world x_m/y_m in Export JSON and get_map.

Needs a Home Assistant restart after updating.