Add Manhattan 3D fire flow simulation

[Nif00]

What changed

• Replaced the Polatlı working dataset with detailed Manhattan Island OSM building and road data.
• Added 3D building height handling, fire-highlighted buildings, visible node pins, and smoother local flow lines.
• Added QUIC-URB-inspired urban wind/flow modeling and a selected-area flow visualization.
• Improved keyboard controls and UI focus behavior.

Validation

• python -m pytest -q — 17 passed.
• Oversized Manhattan JSON artifacts are tracked with Git LFS.