feat: Add persistent localStorage for Kabelstrecken (polylines) visibility

- Add kabelstreckenVisible state with localStorage persistence
- Implement dual localStorage variables (kabelstreckenVisible + polylineVisible) for compatibility
- Add event system for cross-component polyline visibility updates
- Update MapComponent to listen for polylineVisibilityChanged events
- Ensure polylines display correctly on browser reload
- Migrate from Redux-only state to localStorage-first approach
- Add comprehensive debug logging for troubleshooting

Fixes issue where Kabelstrecken checkbox state was lost on page reload
and polylines were not displayed until manual toggle.

components/mainComponent/MapComponent.js

@@ -635,11 +635,40 @@ const MapComponent = ({ locations, onLocationUpdate, lineCoordinates }) => {
 
   //--------------------------------------------
   //  Beim ersten Client-Render den Wert aus localStorage laden
+  //  Prüfe beide localStorage-Variablen (neue und alte)
   useEffect(() => {
-    const storedPolylineVisible = localStorage.getItem("polylineVisible") === "true";
+    let storedPolylineVisible = localStorage.getItem("kabelstreckenVisible") === "true";
+
+    // Fallback auf alte Variable, falls neue nicht existiert
+    if (localStorage.getItem("kabelstreckenVisible") === null) {
+      const oldValue = localStorage.getItem("polylineVisible") === "true";
+      storedPolylineVisible = oldValue;
+      // Migriere zur neuen Variable
+      localStorage.setItem("kabelstreckenVisible", oldValue.toString());
+    }
+
+    console.log(
+      "🔄 MapComponent: Loading polylineVisible from localStorage:",
+      storedPolylineVisible
+    );
     dispatch(setPolylineVisible(storedPolylineVisible));
   }, [dispatch]);
   //--------------------------------------------
+  // Event-Listener für Polyline-Sichtbarkeitsänderungen
+  useEffect(() => {
+    const handlePolylineVisibilityChange = () => {
+      const storedValue = localStorage.getItem("kabelstreckenVisible") === "true";
+      console.log("🔄 MapComponent: Received polylineVisibilityChanged event, value:", storedValue);
+      dispatch(setPolylineVisible(storedValue));
+    };
+
+    window.addEventListener("polylineVisibilityChanged", handlePolylineVisibilityChange);
+
+    return () => {
+      window.removeEventListener("polylineVisibilityChanged", handlePolylineVisibilityChange);
+    };
+  }, [dispatch]);
+  //--------------------------------------------
   useEffect(() => {
     if (statusStaticDistrict === "idle") {
       dispatch(fetchGisStationsStaticDistrictThunk());