Calculating the distance (#255)

* migra for distance

* adding distance calculator

* adding ability to store home address

* improve distance calculation

* calculating distance

* show distance in grid view

* upgrading dependencies

* moving to react 19

* ability to clone a job

* fixing tests

* polishing

lib/services/listings/distanceCalculator.js

@@ -0,0 +1,35 @@
+/*
+ * Copyright (c) 2026 by Christian Kellner.
+ * Licensed under Apache-2.0 with Commons Clause and Attribution/Naming Clause
+ */
+
+const R = 6371000; // Earth radius in meters
+/**
+ * Calculate the great-circle distance between two points on Earth using the Haversine formula.
+ * This is to calculate the distance between the listing address & the address provided by the user. I know, it is only
+ * a rough estimation as this calculates the distance as a straight line, but it's more convenient than using an external
+ * service and still gives a good approximation for sorting purposes.
+ * Returns distance in meters.
+ *
+ * @param {number} lat1
+ * @param {number} lon1
+ * @param {number} lat2
+ * @param {number} lon2
+ * @returns {number}
+ */
+export function distanceMeters(lat1, lon1, lat2, lon2) {
+  const toRad = (deg) => (deg * Math.PI) / 180;
+
+  const phi1 = toRad(lat1);
+  const phi2 = toRad(lat2);
+  const dPhi = toRad(lat2 - lat1);
+  const dLambda = toRad(lon2 - lon1);
+
+  const a =
+    Math.sin(dPhi / 2) * Math.sin(dPhi / 2) +
+    Math.cos(phi1) * Math.cos(phi2) * Math.sin(dLambda / 2) * Math.sin(dLambda / 2);
+
+  const c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
+
+  return Math.round(R * c * 10) / 10;
+}