feat: Buchungsformular merkt sich Benutzerdaten

- Name, E-Mail und Telefonnummer werden in localStorage gespeichert
- Beim nächsten Besuch werden die Felder automatisch ausgefüllt
- Verbessert die User Experience für wiederkehrende Buchungen

src/client/components/booking-form.tsx

@@ -14,6 +14,48 @@ export function BookingForm() {
   const [inspirationPhoto, setInspirationPhoto] = useState<string>("");
   const [photoPreview, setPhotoPreview] = useState<string>("");
   const [errorMessage, setErrorMessage] = useState<string>("");
+  const [isInitialized, setIsInitialized] = useState(false);
+
+  // Load saved customer data from localStorage on mount
+  useEffect(() => {
+    const savedName = localStorage.getItem("bookingForm_customerName");
+    const savedEmail = localStorage.getItem("bookingForm_customerEmail");
+    const savedPhone = localStorage.getItem("bookingForm_customerPhone");
+    
+    if (savedName) setCustomerName(savedName);
+    if (savedEmail) setCustomerEmail(savedEmail);
+    if (savedPhone) setCustomerPhone(savedPhone);
+    
+    setIsInitialized(true);
+  }, []);
+
+  // Save customer data to localStorage when it changes (after initial load)
+  useEffect(() => {
+    if (!isInitialized) return;
+    if (customerName) {
+      localStorage.setItem("bookingForm_customerName", customerName);
+    } else {
+      localStorage.removeItem("bookingForm_customerName");
+    }
+  }, [customerName, isInitialized]);
+
+  useEffect(() => {
+    if (!isInitialized) return;
+    if (customerEmail) {
+      localStorage.setItem("bookingForm_customerEmail", customerEmail);
+    } else {
+      localStorage.removeItem("bookingForm_customerEmail");
+    }
+  }, [customerEmail, isInitialized]);
+
+  useEffect(() => {
+    if (!isInitialized) return;
+    if (customerPhone) {
+      localStorage.setItem("bookingForm_customerPhone", customerPhone);
+    } else {
+      localStorage.removeItem("bookingForm_customerPhone");
+    }
+  }, [customerPhone, isInitialized]);
 
   const { data: treatments } = useQuery(
     queryClient.treatments.live.list.experimental_liveOptions()