feat: Persist checkbox states in localStorage to retain settings after page reload

- Implemented logic to save the visibility states of POI and map layers in localStorage.
- Loaded saved checkbox states on component mount to retain user preferences.
- Updated `handleCheckboxChange` and `handlePoiCheckboxChange` to store changes in localStorage.
- Ensured that settings persist across page reloads for a better user experience.

websocket-server.js

@@ -7,8 +7,22 @@ wss.on("connection", (ws) => {
   console.log("New WebSocket connection");
 
   ws.on("message", (message) => {
-    console.log("Received:", message);
-    ws.send(JSON.stringify({ message: "Hallo vom WebSocket-Server" }));
+    // Konvertiere den Buffer in einen String
+    const messageString = message.toString();
+
+    console.log("Received:", messageString);
+
+    // Versuche die Nachricht in JSON zu parsen
+    try {
+      const parsedMessage = JSON.parse(messageString);
+
+      // Beispielnachricht an den Client zurücksenden
+      if (parsedMessage.type === "test") {
+        ws.send(JSON.stringify({ message: `Hallo zurück, ${parsedMessage.message}` }));
+      }
+    } catch (error) {
+      console.error("Fehler beim Parsen der Nachricht:", error);
+    }
   });
 
   ws.on("close", () => {