feat(auth): add user invitation flow with account setup

- add `createAccountSetup`, `verifyAccountSetupToken`, `deleteAccountSetupToken` to verifications core
- add `completeAccountSetup` function to auth core for password creation on invite
- add `InvitationEmail` template for sending invite links
- add `SetupAccountPage` client page for invited users to set their password
- add `UserCreateModal` admin component to invite new users
- wire invitation action and API endpoint in auth feature
- update admin `UsersPage` to include user creation modal
- update auth and admin README docs

src/features/admin/components/UserCreateModal.client.js

@@ -0,0 +1,157 @@
+'use client';
+
+import { useState, useEffect } from 'react';
+import { Input, TagInput, Modal, RoleBadge } from '@zen/core/shared/components';
+import { useToast } from '@zen/core/toast';
+
+const UserCreateModal = ({ isOpen, onClose, onSaved }) => {
+    const toast = useToast();
+    const [saving, setSaving] = useState(false);
+    const [allRoles, setAllRoles] = useState([]);
+    const [selectedRoleIds, setSelectedRoleIds] = useState([]);
+    const [formData, setFormData] = useState({ name: '', email: '', password: '' });
+    const [errors, setErrors] = useState({});
+    const [error, setError] = useState('');
+
+    useEffect(() => {
+        if (!isOpen) return;
+        setFormData({ name: '', email: '', password: '' });
+        setSelectedRoleIds([]);
+        setErrors({});
+        setError('');
+        fetchRoles();
+    }, [isOpen]);
+
+    const fetchRoles = async () => {
+        try {
+            const res = await fetch('/zen/api/roles', { credentials: 'include' });
+            const data = await res.json();
+            setAllRoles(data.roles || []);
+        } catch {
+            toast.error('Impossible de charger les rôles');
+        }
+    };
+
+    const handleInputChange = (field, value) => {
+        setFormData(prev => ({ ...prev, [field]: value }));
+        if (errors[field]) setErrors(prev => ({ ...prev, [field]: null }));
+        if (error) setError('');
+    };
+
+    const validate = () => {
+        const newErrors = {};
+        if (!formData.name.trim()) newErrors.name = 'Le nom est requis';
+        if (!formData.email.trim()) newErrors.email = 'Le courriel est requis';
+        setErrors(newErrors);
+        return Object.keys(newErrors).length === 0;
+    };
+
+    const handleSubmit = async () => {
+        if (!validate()) return;
+        setSaving(true);
+        setError('');
+        try {
+            const res = await fetch('/zen/api/users', {
+                method: 'POST',
+                headers: { 'Content-Type': 'application/json' },
+                credentials: 'include',
+                body: JSON.stringify({
+                    name: formData.name.trim(),
+                    email: formData.email.trim(),
+                    password: formData.password || undefined,
+                    roleIds: selectedRoleIds,
+                }),
+            });
+            const data = await res.json();
+            if (!res.ok) {
+                setError(data.message || data.error || "Impossible de créer l'utilisateur");
+                return;
+            }
+            if (data.invited) {
+                toast.success('Utilisateur créé — invitation envoyée par courriel');
+            } else {
+                toast.success('Utilisateur créé');
+            }
+            onSaved?.();
+            onClose();
+        } catch {
+            setError("Impossible de créer l'utilisateur");
+        } finally {
+            setSaving(false);
+        }
+    };
+
+    const roleOptions = allRoles.map(r => ({
+        value: r.id,
+        label: r.name,
+        color: r.color || '#6b7280',
+        description: r.description || undefined,
+    }));
+
+    return (
+        <Modal
+            isOpen={isOpen}
+            onClose={onClose}
+            title="Nouvel utilisateur"
+            onSubmit={handleSubmit}
+            submitLabel="Créer"
+            loading={saving}
+            size="md"
+        >
+            <div className="flex flex-col gap-4">
+                {error && (
+                    <div className="p-3 bg-red-50 border border-red-200 rounded-lg dark:bg-red-500/10 dark:border-red-500/20">
+                        <div className="flex items-center gap-2">
+                            <div className="w-1.5 h-1.5 bg-red-500 rounded-full flex-shrink-0" />
+                            <span className="text-xs text-red-700 dark:text-red-400">{error}</span>
+                        </div>
+                    </div>
+                )}
+
+                <div className="grid grid-cols-1 sm:grid-cols-2 gap-4">
+                    <Input
+                        label="Nom complet *"
+                        value={formData.name}
+                        onChange={(value) => handleInputChange('name', value)}
+                        placeholder="Prénom Nom"
+                        error={errors.name}
+                    />
+                    <Input
+                        label="Courriel *"
+                        type="email"
+                        value={formData.email}
+                        onChange={(value) => handleInputChange('email', value)}
+                        placeholder="utilisateur@exemple.com"
+                        error={errors.email}
+                    />
+                </div>
+
+                <TagInput
+                    label="Rôles"
+                    options={roleOptions}
+                    value={selectedRoleIds}
+                    onChange={setSelectedRoleIds}
+                    placeholder="Rechercher un rôle..."
+                    renderTag={(opt, onRemove) => (
+                        <RoleBadge key={opt.value} name={opt.label} color={opt.color} onRemove={onRemove} />
+                    )}
+                />
+
+                <div className="flex flex-col gap-1">
+                    <Input
+                        label="Mot de passe"
+                        type="password"
+                        value={formData.password}
+                        onChange={(value) => handleInputChange('password', value)}
+                        placeholder="Laisser vide pour envoyer une invitation"
+                    />
+                    <p className="text-xs text-neutral-500 dark:text-neutral-400">
+                        Si vide, un courriel d'invitation sera envoyé pour que l'utilisateur crée son mot de passe.
+                    </p>
+                </div>
+            </div>
+        </Modal>
+    );
+};
+
+export default UserCreateModal;

src/features/admin/components/index.js

@@ -7,3 +7,4 @@ export { default as AdminHeader } from './AdminHeader.js';
 export { default as ThemeToggle } from './ThemeToggle.js';
 export { default as UserEditModal } from './UserEditModal.client.js';
 export { default as RoleEditModal } from './RoleEditModal.client.js';
+export { default as UserCreateModal } from './UserCreateModal.client.js';