feat: add duplicate email detection via auth hook with fallback

- Add before-user-created hook function for server-side duplicate email detection
- Implement fallback detection using identities array check (Supabase limitation)
- Update signUpWithPassword to detect duplicate emails via hook errors or empty identities
- Add error handling in login page to show duplicate email errors and auto-switch to login mode
- Add auth hook setup documentation and test scripts
- Add password reset and update password flows
- Add email templates for signup confirmation and password reset

scripts/setup-auth-hook.ts

@@ -0,0 +1,95 @@
+#!/usr/bin/env tsx
+/**
+ * Setup Script: Configure Auth Hook Link
+ *
+ * Dit script configureert de link tussen Supabase Auth Hook en onze Postgres functie.
+ *
+ * Helaas ondersteunt Supabase Management API nog geen Auth Hooks configuratie,
+ * dus dit script geeft instructies voor handmatige configuratie.
+ *
+ * In de toekomst kan dit worden geautomatiseerd zodra Supabase API dit ondersteunt.
+ */
+
+import { config } from 'dotenv'
+import { createClient } from '@supabase/supabase-js'
+
+// Load environment variables from .env.local
+config({ path: '.env.local' })
+
+const supabaseUrl = process.env.NEXT_PUBLIC_SUPABASE_URL!
+const supabaseServiceKey = process.env.SUPABASE_SERVICE_ROLE_KEY!
+
+if (!supabaseUrl || !supabaseServiceKey) {
+  console.error('❌ Missing environment variables')
+  console.error('   Make sure .env.local is loaded with:')
+  console.error('   - NEXT_PUBLIC_SUPABASE_URL')
+  console.error('   - SUPABASE_SERVICE_ROLE_KEY')
+  process.exit(1)
+}
+
+const supabase = createClient(supabaseUrl, supabaseServiceKey, {
+  auth: {
+    autoRefreshToken: false,
+    persistSession: false
+  }
+})
+
+async function setupAuthHook() {
+  console.log('🔐 Auth Hook Setup Script\n')
+
+  // Extract project ID from URL
+  const projectId = supabaseUrl.match(/https:\/\/([^.]+)\.supabase\.co/)?.[1]
+
+  // Check if function exists by trying to call it with a test payload
+  // This is more reliable than querying pg_proc directly
+  try {
+    const testPayload = {
+      user: {
+        email: 'test@example.com'
+      }
+    }
+
+    const { data, error } = await supabase.rpc('hook_check_duplicate_email', {
+      event: testPayload
+    })
+
+    // If function doesn't exist, we'll get a "function does not exist" error
+    if (error && error.message?.includes('does not exist')) {
+      console.error('❌ Function niet gevonden:', error.message)
+      console.log('\n📝 Stap 1: Run eerst de migration:')
+      console.log('   1. Ga naar: https://supabase.com/dashboard/project/' + projectId + '/sql')
+      console.log('   2. Open migration file: supabase/migrations/20251119094908_auth_hook_duplicate_email.sql')
+      console.log('   3. Kopieer de inhoud en plak in SQL Editor')
+      console.log('   4. Klik "RUN" om de functie aan te maken')
+      console.log('\n   Of via CLI (als je Supabase CLI hebt geconfigureerd):')
+      console.log('   npx supabase db push')
+      return
+    }
+
+    console.log('✅ Function exists: hook_check_duplicate_email')
+    console.log('   Test call succeeded with response:', data || '{}')
+
+  } catch (error: any) {
+    console.error('⚠️  Could not verify function:', error.message)
+    console.log('   Continuing with setup instructions...\n')
+  }
+
+  console.log('\n📝 Stap 2: Configureer hook link in Supabase Dashboard:')
+  console.log('   1. Ga naar: https://supabase.com/dashboard/project/' + projectId + '/auth/hooks')
+  console.log('   2. Klik "Add a new hook" of "Enable Hooks"')
+  console.log('   3. Selecteer:')
+  console.log('      - Hook Type: "Send a hook on before a user is created" (before-user-created)')
+  console.log('      - Select hook: "Postgres Function"')
+  console.log('      - Schema: "public"')
+  console.log('      - Function Name: "hook_check_duplicate_email"')
+  console.log('   4. Klik "Create hook" of "Save"')
+  console.log('\n💡 Tip: Deze stap moet handmatig omdat Supabase Management API')
+  console.log('   Auth Hooks configuratie nog niet ondersteunt.')
+  console.log('\n✅ Setup compleet na Dashboard configuratie!')
+  console.log('\n🧪 Test de hook:')
+  console.log('   1. Ga naar je signup pagina')
+  console.log('   2. Probeer te registreren met een bestaand emailadres')
+  console.log('   3. Je zou een error moeten zien: "Dit emailadres is al geregistreerd..."')
+}
+
+setupAuthHook().catch(console.error)