feat: add auto-lookup and duplicate check for WSDC registration

Enhanced WSDC registration flow with auto-lookup and account validation:

Backend changes:
- Add accountExists flag to WSDC lookup endpoint
- Check database for existing users with WSDC ID
- Fix Prisma binary target for Alpine Linux Docker containers

Frontend changes:
- Auto-lookup WSDC data after entering 4+ digits (500ms debounce)
- Show live preview dropdown with dancer information
- Display warning if account with WSDC ID already exists
- Block registration and suggest login for existing accounts
- Improve UX with real-time validation feedback
- Add CheckCircle, XCircle, AlertCircle icons for visual feedback

This prevents duplicate WSDC ID registrations and provides immediate
feedback to users, improving the registration experience.

Tested with:
- ID 26111 (Vince Yap) - new account allowed
- ID 26997 (Radoslaw) - existing account blocked

backend/prisma/schema.prisma

@@ -2,7 +2,8 @@
 // Database: PostgreSQL 15
 
 generator client {
-  provider = "prisma-client-js"
+  provider      = "prisma-client-js"
+  binaryTargets = ["native", "linux-musl-openssl-3.0.x"]
 }
 
 datasource db {

backend/src/controllers/wsdc.js

@@ -3,6 +3,7 @@
  * Provides proxy endpoint for World Swing Dance Council (WSDC) dancer lookup
  */
 
+const { prisma } = require('../utils/db');
 const WSDC_API_BASE = 'https://points.worldsdc.com/lookup2020/find';
 
 /**
@@ -61,9 +62,15 @@ exports.lookupDancer = async (req, res) => {
       dominateRole: data.dominate_data?.short_dominate_role || null
     };
 
+    // Check if user with this WSDC ID already exists in our database
+    const existingUser = await prisma.user.findUnique({
+      where: { wsdcId: String(data.dancer_wsdcid) }
+    });
+
     return res.status(200).json({
       success: true,
-      dancer: dancerData
+      dancer: dancerData,
+      accountExists: !!existingUser
     });
 
   } catch (error) {

frontend/src/pages/RegisterPage.jsx

@@ -1,8 +1,8 @@
-import { useState } from 'react';
+import { useState, useEffect } from 'react';
 import { useNavigate, Link } from 'react-router-dom';
 import { useAuth } from '../contexts/AuthContext';
 import { wsdcAPI } from '../services/api';
-import { Video, Mail, Lock, User, Hash, ArrowRight, ArrowLeft, Loader2 } from 'lucide-react';
+import { Video, Mail, Lock, User, Hash, ArrowRight, ArrowLeft, Loader2, CheckCircle, XCircle, AlertCircle } from 'lucide-react';
 import PasswordStrengthIndicator from '../components/common/PasswordStrengthIndicator';
 
 const RegisterPage = () => {
@@ -13,6 +13,8 @@ const RegisterPage = () => {
   const [hasWsdcId, setHasWsdcId] = useState(null);
   const [wsdcId, setWsdcId] = useState('');
   const [wsdcData, setWsdcData] = useState(null);
+  const [wsdcPreview, setWsdcPreview] = useState(null); // Preview data after 4+ digits
+  const [accountExists, setAccountExists] = useState(false); // Check if account exists
   const [wsdcLoading, setWsdcLoading] = useState(false);
   const [wsdcError, setWsdcError] = useState('');
 
@@ -31,35 +33,68 @@ const RegisterPage = () => {
   const { register } = useAuth();
   const navigate = useNavigate();
 
-  // Handle WSDC ID lookup
+  // Auto-lookup WSDC ID after 4+ digits are entered
-  const handleWsdcLookup = async () => {
+  useEffect(() => {
-    if (!wsdcId || wsdcId.trim() === '') {
+    const lookupWsdcId = async () => {
-      setWsdcError('Please enter your WSDC ID');
+      if (wsdcId.length >= 4 && /^\d+$/.test(wsdcId)) {
+        setWsdcLoading(true);
+        setWsdcError('');
+        setWsdcPreview(null);
+        setAccountExists(false);
+
+        try {
+          const response = await wsdcAPI.lookupDancer(wsdcId);
+
+          if (response.success && response.dancer) {
+            setWsdcPreview(response.dancer);
+            setAccountExists(response.accountExists || false);
+
+            if (!response.accountExists) {
+              setWsdcError('');
+            }
+          }
+        } catch (err) {
+          setWsdcPreview(null);
+          setAccountExists(false);
+          if (err.status === 404) {
+            setWsdcError('WSDC ID not found in the registry');
+          } else {
+            setWsdcError('');
+          }
+        } finally {
+          setWsdcLoading(false);
+        }
+      } else {
+        setWsdcPreview(null);
+        setAccountExists(false);
+        setWsdcError('');
+      }
+    };
+
+    const timeoutId = setTimeout(lookupWsdcId, 500); // Debounce 500ms
+    return () => clearTimeout(timeoutId);
+  }, [wsdcId]);
+
+  // Handle WSDC ID confirmation and continue to registration
+  const handleWsdcContinue = () => {
+    if (!wsdcPreview) {
+      setWsdcError('Please enter a valid WSDC ID');
       return;
     }
 
-    setWsdcLoading(true);
+    if (accountExists) {
-    setWsdcError('');
+      setWsdcError('An account with this WSDC ID already exists');
-
+      return;
-    try {
-      const response = await wsdcAPI.lookupDancer(wsdcId);
-
-      if (response.success && response.dancer) {
-        setWsdcData(response.dancer);
-        setFormData(prev => ({
-          ...prev,
-          firstName: response.dancer.firstName,
-          lastName: response.dancer.lastName,
-        }));
-        setStep(2);
-      } else {
-        setWsdcError('WSDC ID not found. Please check and try again.');
-      }
-    } catch (err) {
-      setWsdcError(err.data?.message || 'Failed to lookup WSDC ID. Please try again.');
-    } finally {
-      setWsdcLoading(false);
     }
+
+    // Set data and move to registration form
+    setWsdcData(wsdcPreview);
+    setFormData(prev => ({
+      ...prev,
+      firstName: wsdcPreview.firstName,
+      lastName: wsdcPreview.lastName,
+    }));
+    setStep(2);
   };
 
   // Handle "No WSDC ID" option
@@ -158,39 +193,84 @@ const RegisterPage = () => {
                   <input
                     type="text"
                     value={wsdcId}
-                    onChange={(e) => setWsdcId(e.target.value)}
+                    onChange={(e) => setWsdcId(e.target.value.replace(/\D/g, ''))}
                     className="pl-10 block w-full px-3 py-2 border border-gray-300 rounded-md shadow-sm focus:ring-primary-500 focus:border-primary-500"
                     placeholder="26997"
-                    disabled={wsdcLoading}
+                    maxLength={10}
                   />
+                  {wsdcLoading && (
+                    <div className="absolute inset-y-0 right-0 pr-3 flex items-center pointer-events-none">
+                      <Loader2 className="h-5 w-5 text-gray-400 animate-spin" />
+                    </div>
+                  )}
                 </div>
-                {wsdcError && (
+
-                  <p className="mt-2 text-sm text-red-600">{wsdcError}</p>
+                {/* Preview dropdown - shows after 4 digits */}
+                {wsdcId.length >= 4 && wsdcPreview && !wsdcLoading && (
+                  <div className="mt-3 border border-gray-200 rounded-md p-4 bg-gray-50">
+                    <div className="flex items-start justify-between">
+                      <div className="flex-1">
+                        <div className="flex items-center gap-2 mb-2">
+                          <CheckCircle className="h-5 w-5 text-green-500" />
+                          <span className="font-medium text-gray-900">Dancer found</span>
+                        </div>
+                        <div className="space-y-1 text-sm">
+                          <p><span className="text-gray-600">WSDC ID:</span> <span className="font-medium">{wsdcPreview.wsdcId}</span></p>
+                          <p><span className="text-gray-600">Name:</span> <span className="font-medium">{wsdcPreview.firstName} {wsdcPreview.lastName}</span></p>
+                        </div>
+                      </div>
+                    </div>
+
+                    {accountExists && (
+                      <div className="mt-3 p-3 bg-red-50 border border-red-200 rounded-md flex items-start gap-2">
+                        <XCircle className="h-5 w-5 text-red-500 flex-shrink-0 mt-0.5" />
+                        <div className="flex-1">
+                          <p className="text-sm font-medium text-red-800">Account already exists</p>
+                          <p className="text-sm text-red-600 mt-1">
+                            An account with this WSDC ID is already registered.
+                            <Link to="/login" className="font-medium underline ml-1">Sign in instead</Link>
+                          </p>
+                        </div>
+                      </div>
+                    )}
+
+                    {!accountExists && (
+                      <div className="mt-3 p-2 bg-green-50 border border-green-200 rounded-md flex items-center gap-2">
+                        <CheckCircle className="h-4 w-4 text-green-600 flex-shrink-0" />
+                        <p className="text-sm text-green-700">
+                          Looks good! Click Continue to proceed.
+                        </p>
+                      </div>
+                    )}
+                  </div>
+                )}
+
+                {wsdcError && !wsdcPreview && (
+                  <div className="mt-3 p-3 bg-yellow-50 border border-yellow-200 rounded-md flex items-start gap-2">
+                    <AlertCircle className="h-5 w-5 text-yellow-600 flex-shrink-0 mt-0.5" />
+                    <p className="text-sm text-yellow-800">{wsdcError}</p>
+                  </div>
                 )}
               </div>
 
               <div className="space-y-3">
                 <button
-                  onClick={handleWsdcLookup}
+                  onClick={handleWsdcContinue}
-                  disabled={wsdcLoading}
+                  disabled={!wsdcPreview || accountExists || wsdcLoading}
-                  className="w-full flex items-center justify-center gap-2 py-2 px-4 border border-transparent rounded-md shadow-sm text-white bg-primary-600 hover:bg-primary-700 focus:outline-none focus:ring-2 focus:ring-offset-2 focus:ring-primary-500 disabled:opacity-50 font-medium"
+                  className="w-full flex items-center justify-center gap-2 py-2 px-4 border border-transparent rounded-md shadow-sm text-white bg-primary-600 hover:bg-primary-700 focus:outline-none focus:ring-2 focus:ring-offset-2 focus:ring-primary-500 disabled:opacity-50 disabled:cursor-not-allowed font-medium"
                 >
-                  {wsdcLoading ? (
+                  Continue
-                    <>
+                  <ArrowRight className="w-5 h-5" />
-                      <Loader2 className="w-5 h-5 animate-spin" />
-                      Looking up...
-                    </>
-                  ) : (
-                    <>
-                      Continue
-                      <ArrowRight className="w-5 h-5" />
-                    </>
-                  )}
                 </button>
 
                 <button
-                  onClick={() => setHasWsdcId(null)}
+                  onClick={() => {
-                  disabled={wsdcLoading}
+                    setHasWsdcId(null);
+                    setWsdcId('');
+                    setWsdcPreview(null);
+                    setAccountExists(false);
+                    setWsdcError('');
+                  }}
                   className="w-full py-2 px-4 border border-gray-300 rounded-md text-gray-700 hover:bg-gray-50 font-medium"
                 >
                   <ArrowLeft className="w-5 h-5 inline mr-2" />