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/set-password/page.tsx

@@ -0,0 +1,108 @@
+'use client'
+
+import { useState } from 'react'
+import { useRouter } from 'next/navigation'
+import { updateUserPassword } from '@/lib/auth/client'
+
+export default function SetPasswordPage() {
+    const router = useRouter()
+    const [password, setPassword] = useState('')
+    const [confirmPassword, setConfirmPassword] = useState('')
+    const [loading, setLoading] = useState(false)
+    const [error, setError] = useState('')
+
+    async function handleSetPassword(e: React.FormEvent) {
+        e.preventDefault()
+        setError('')
+
+        if (password !== confirmPassword) {
+            setError('Wachtwoorden komen niet overeen')
+            return
+        }
+
+        if (password.length < 8) {
+            setError('Wachtwoord minimaal 8 tekens')
+            return
+        }
+
+        setLoading(true)
+
+        try {
+            await updateUserPassword(password)
+            router.push('/epd/clients')
+        } catch (err: any) {
+            setError(err.message)
+        } finally {
+            setLoading(false)
+        }
+    }
+
+    function handleSkip() {
+        router.push('/epd/clients')
+    }
+
+    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">
+                <h1 className="text-2xl font-bold text-slate-900 mb-2">
+                    Stel een Wachtwoord In (Optioneel)
+                </h1>
+                <p className="text-slate-600 mb-6">
+                    Met een wachtwoord kun je sneller inloggen zonder magic link.
+                </p>
+
+                {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={handleSetPassword} className="space-y-4">
+                    <div>
+                        <label className="block text-sm font-medium text-slate-700 mb-1">
+                            Wachtwoord
+                        </label>
+                        <input
+                            type="password"
+                            value={password}
+                            onChange={(e) => setPassword(e.target.value)}
+                            placeholder="Min. 8 tekens"
+                            minLength={8}
+                            className="w-full px-4 py-2.5 border border-slate-300 rounded-lg focus:ring-2 focus:ring-teal-500"
+                        />
+                    </div>
+
+                    <div>
+                        <label className="block text-sm font-medium text-slate-700 mb-1">
+                            Bevestig Wachtwoord
+                        </label>
+                        <input
+                            type="password"
+                            value={confirmPassword}
+                            onChange={(e) => setConfirmPassword(e.target.value)}
+                            placeholder="••••••••"
+                            minLength={8}
+                            className="w-full px-4 py-2.5 border border-slate-300 rounded-lg focus:ring-2 focus:ring-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 disabled:opacity-50"
+                    >
+                        {loading ? 'Instellen...' : 'Wachtwoord Instellen'}
+                    </button>
+
+                    <button
+                        type="button"
+                        onClick={handleSkip}
+                        className="w-full text-slate-600 hover:text-slate-900 text-sm font-medium py-2"
+                    >
+                        Sla over (blijf magic link gebruiken)
+                    </button>
+                </form>
+            </div>
+        </div>
+    )
+}