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/auth/email.js

@@ -6,6 +6,7 @@ import { PasswordResetEmail } from './templates/PasswordResetEmail.js';
 import { PasswordChangedEmail } from './templates/PasswordChangedEmail.js';
 import { EmailChangeConfirmEmail } from './templates/EmailChangeConfirmEmail.js';
 import { EmailChangeNotifyEmail } from './templates/EmailChangeNotifyEmail.js';
+import { InvitationEmail } from './templates/InvitationEmail.js';
 
 export { createEmailVerification, verifyEmailToken, createPasswordReset, verifyResetToken, deleteResetToken }
   from '../../core/users/verifications.js';
@@ -93,4 +94,17 @@ async function sendEmailChangeNewNotifyEmail(newEmail, oldEmail) {
   return result;
 }
 
-export { sendVerificationEmail, sendPasswordResetEmail, sendPasswordChangedEmail, sendEmailChangeConfirmEmail, sendEmailChangeOldNotifyEmail, sendEmailChangeNewNotifyEmail };
+async function sendInvitationEmail(email, token, baseUrl) {
+  const appName = process.env.ZEN_NAME || 'ZEN';
+  const setupUrl = `${baseUrl}/auth/setup?email=${encodeURIComponent(email)}&token=${token}`;
+  const html = await render(<InvitationEmail setupUrl={setupUrl} companyName={appName} />);
+  const result = await sendEmail({ to: email, subject: `Terminez la création de votre compte – ${appName}`, html });
+  if (!result.success) {
+    fail(`Auth: failed to send invitation email to ${email}: ${result.error}`);
+    throw new Error('Failed to send invitation email');
+  }
+  info(`Auth: invitation email sent to ${email}`);
+  return result;
+}
+
+export { sendVerificationEmail, sendPasswordResetEmail, sendPasswordChangedEmail, sendEmailChangeConfirmEmail, sendEmailChangeOldNotifyEmail, sendEmailChangeNewNotifyEmail, sendInvitationEmail };