init: rough companion app stub

lib/domain/models/position.dart

@@ -0,0 +1,25 @@
+// Normalised coordinates: x and y are in the range 0..1 relative to the floor plan canvas.
+class Position {
+  const Position({required this.x, required this.y});
+
+  final double x;
+  final double y;
+
+  Position copyWith({double? x, double? y}) =>
+      Position(x: x ?? this.x, y: y ?? this.y);
+
+  // Key names should match localiserd API fields.
+  Map<String, dynamic> toJson() => {'x': x, 'y': y};
+
+  factory Position.fromJson(Map<String, dynamic> json) => Position(
+        x: (json['x'] as num).toDouble(),
+        y: (json['y'] as num).toDouble(),
+      );
+
+  @override
+  bool operator ==(Object other) =>
+      other is Position && other.x == x && other.y == y;
+
+  @override
+  int get hashCode => Object.hash(x, y);
+}