feat: Set default polyline visibility to true if not defined in localStorage

- Added logic to check if 'polylineVisible' exists in localStorage on page load.
- If not present, set the default value to 'true' to ensure polylines are displayed by default.
- Updated `setupPolylines` function to handle polyline visibility based on localStorage value.

utils/setupPolylines.js

@@ -47,7 +47,13 @@ export function enablePolylineEvents(polylines, lineColors) {
 }
 
 export const setupPolylines = (map, linePositions, lineColors, tooltipContents, setNewCoords, tempMarker, currentZoom, currentCenter, polylineVisible) => {
-  polylineVisible = localStorage.getItem("polylineVisible") === "true";
+  if (localStorage.getItem("polylineVisible") === null) {
+    localStorage.setItem("polylineVisible", "true"); // Standardwert setzen
+    polylineVisible = true; // Wert in der Funktion initialisieren
+  } else {
+    polylineVisible = localStorage.getItem("polylineVisible") === "true";
+  }
+
   if (!polylineVisible) {
     // Entferne alle Polylinien, wenn sie ausgeblendet werden sollen
     if (window.polylines) {