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

app/reset-password/page.tsx

@@ -0,0 +1,105 @@
+'use client'
+
+import { useState } from 'react'
+import { resetPasswordForEmail } from '@/lib/auth/client'
+import Link from 'next/link'
+
+export default function ResetPasswordPage() {
+  const [email, setEmail] = useState('')
+  const [loading, setLoading] = useState(false)
+  const [sent, setSent] = useState(false)
+  const [error, setError] = useState('')
+
+  async function handleResetRequest(e: React.FormEvent) {
+    e.preventDefault()
+    setLoading(true)
+    setError('')
+
+    try {
+      await resetPasswordForEmail(email)
+      setSent(true)
+    } catch (err: any) {
+      setError(err.message || 'Er ging iets mis')
+    } finally {
+      setLoading(false)
+    }
+  }
+
+  if (sent) {
+    return (
+      <div className="min-h-screen flex items-center justify-center bg-slate-50 px-4">
+        <div className="max-w-md w-full bg-white p-8 rounded-lg shadow-sm text-center space-y-4">
+          <div className="text-5xl mb-4">✉️</div>
+          <h1 className="text-2xl font-bold text-slate-900">Email Verstuurd!</h1>
+          <p className="text-slate-600">
+            Check je inbox voor de reset link. De link is 1 uur geldig.
+          </p>
+          <p className="text-sm text-slate-500">
+            Niet ontvangen? Check je spam folder.
+          </p>
+          <Link
+            href="/login"
+            className="inline-block mt-4 text-teal-600 hover:text-teal-700 font-medium"
+          >
+            ← Terug naar login
+          </Link>
+        </div>
+      </div>
+    )
+  }
+
+  return (
+    <div className="min-h-screen flex items-center justify-center bg-slate-50 px-4">
+      <div className="max-w-md w-full bg-white p-8 rounded-lg shadow-sm">
+        <div className="mb-6">
+          <h1 className="text-2xl font-bold text-slate-900 mb-2">
+            Wachtwoord Vergeten?
+          </h1>
+          <p className="text-slate-600">
+            Geen probleem! Vul je email in en we sturen je een reset link.
+          </p>
+        </div>
+
+        {error && (
+          <div className="mb-4 p-3 bg-red-50 border border-red-200 rounded-lg text-red-800 text-sm">
+            {error}
+          </div>
+        )}
+
+        <form onSubmit={handleResetRequest} className="space-y-4">
+          <div>
+            <label className="block text-sm font-medium text-slate-700 mb-1">
+              Email
+            </label>
+            <input
+              type="email"
+              value={email}
+              onChange={(e) => setEmail(e.target.value)}
+              placeholder="jouw@email.nl"
+              required
+              className="w-full px-4 py-2.5 border border-slate-300 rounded-lg focus:ring-2 focus:ring-teal-500 focus:border-teal-500"
+            />
+          </div>
+
+          <button
+            type="submit"
+            disabled={loading}
+            className="w-full bg-teal-600 hover:bg-teal-700 text-white font-medium py-2.5 px-4 rounded-lg transition-colors disabled:opacity-50"
+          >
+            {loading ? 'Verzenden...' : 'Stuur Reset Link'}
+          </button>
+        </form>
+
+        <div className="mt-6 text-center">
+          <Link
+            href="/login"
+            className="text-sm text-slate-600 hover:text-slate-900"
+          >
+            ← Terug naar login
+          </Link>
+        </div>
+      </div>
+    </div>
+  )
+}
+