Add team-only user creation, remove public signup

- Add + New User form on Companies page (name, email, password, company)
- Create-user Supabase edge function with role verification
- Remove public signup route and login page link

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/pages/Login.jsx

@@ -67,8 +67,7 @@ export default function Login() {
         </form>
 
         <p style={{ textAlign: 'center', marginTop: 20, fontSize: 13, color: '#a8a8a8' }}>
-          New client?{' '}
-          <Link to="/signup" style={{ color: 'var(--accent)' }}>Create an account</Link>
+          Contact Fourge Branding to get access.
         </p>
       </div>
     </div>