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

docker-compose.yml

@@ -15,4 +15,5 @@ services:
       retries: 3
       start_period: 40s
     environment:
-      - NODE_ENV=development
+      - NODE_ENV=production
+      - DISABLE_DUPLICATE_CHECK=true