Build curated brewery index page: featured card, nearby list/map sync, recently added

web/frontend/app/features/breweries/utils/distance.ts

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+const EARTH_RADIUS_METRES = 6_371_000;
+
+export interface Coordinates {
+    latitude: number;
+    longitude: number;
+}
+
+export const haversineDistanceMetres = (a: Coordinates, b: Coordinates): number => {
+    const toRadians = (degrees: number) => (degrees * Math.PI) / 180;
+    const deltaLat = toRadians(b.latitude - a.latitude);
+    const deltaLng = toRadians(b.longitude - a.longitude);
+    const lat1 = toRadians(a.latitude);
+    const lat2 = toRadians(b.latitude);
+
+    const h =
+        Math.sin(deltaLat / 2) ** 2 +
+        Math.cos(lat1) * Math.cos(lat2) * Math.sin(deltaLng / 2) ** 2;
+
+    return 2 * EARTH_RADIUS_METRES * Math.asin(Math.sqrt(h));
+};
+
+export const formatDistance = (metres: number): string => {
+    const km = metres / 1000;
+    return km < 10 ? `${km.toFixed(1)} km` : `${Math.round(km)} km`;
+};