Module controller 

MapController — wires a Slint MapView instance to a TileSource.

The controller:

1. Owns the active tile source (boxed, so it’s swappable at runtime).
2. Holds the canonical camera state (centre_lon, centre_lat, zoom) — the Slint properties of the same name are mirrors, updated by MapController::refresh.
3. Translates the pan and zoom-by callbacks the Slint MapView fires (during user gestures) back into camera moves.
4. Pushes the visible-tile model into the MapView after every refresh.

Structs

MapController

Owns the source + camera; refreshes the MapView’s tile model.