Fix: Slot reservation only after successful email validation

- Move email validation before slot reservation in backend
- Remove duplicate frontend email validation
- Slots are no longer blocked by failed booking attempts
- Clean up unused email error UI components
- Ensure slots remain available if email validation fails

src/client/components/booking-form.tsx

@@ -138,7 +138,8 @@ export function BookingForm() {
     if (fileInput) fileInput.value = '';
   };
 
-  const handleSubmit = (e: React.FormEvent) => {
+
+  const handleSubmit = async (e: React.FormEvent) => {
     e.preventDefault();
     setErrorMessage(""); // Clear any previous error messages
     
@@ -160,6 +161,8 @@ export function BookingForm() {
       setErrorMessage("Bitte bestätige die Kenntnisnahme der Allgemeinen Geschäftsbedingungen.");
       return;
     }
+
+    // Email validation now handled in backend before slot reservation
     const slot = availableSlots.find((s) => s.id === selectedSlotId);
     const appointmentTime = slot?.time || "";
     // console.log("Creating booking with data:", {
@@ -206,19 +209,13 @@ export function BookingForm() {
         onError: (error: any) => {
           console.error("Booking error:", error);
           
-          // Extract error message from oRPC error structure
+          // Simple error handling for oRPC errors
           let errorText = "Ein unbekannter Fehler ist aufgetreten.";
           
-          if (error?.message) {
+          if (error?.cause?.message) {
+            errorText = error.cause.message;
+          } else if (error?.message && error.message !== "Internal server error") {
             errorText = error.message;
-          } else if (error?.data?.message) {
-            errorText = error.data.message;
-          } else if (error?.data?.error) {
-            errorText = error.data.error;
-          } else if (typeof error === 'string') {
-            errorText = error;
-          } else if (error?.toString) {
-            errorText = error.toString();
           }
           
           setErrorMessage(errorText);