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/index.js

@@ -9,7 +9,8 @@ export {
   requestPasswordReset,
   resetPassword,
   verifyUserEmail,
-  updateUser
+  updateUser,
+  completeAccountSetup
 } from './auth.js';
 
 export {
@@ -28,7 +29,8 @@ export {
   deleteResetToken,
   sendVerificationEmail,
   sendPasswordResetEmail,
-  sendPasswordChangedEmail
+  sendPasswordChangedEmail,
+  sendInvitationEmail
 } from './email.js';
 
 export {
@@ -46,6 +48,7 @@ export {
   forgotPasswordAction,
   resetPasswordAction,
   verifyEmailAction,
+  setupAccountAction,
   setSessionCookie,
   refreshSessionCookie
 } from './actions.js';