Admin shortcut in the account menu, switched on per study user from /admin; v2.25.0

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

src/components/HeaderAccount.tsx

@@ -6,6 +6,7 @@ interface AccountStatus {
   username: string
   displayName?: string
   avatarUrl?: string
+  adminShortcut?: boolean
 }
 
 // Shared across header instances so moving between pages doesn't flash the signed-out icon
@@ -87,6 +88,9 @@ export function HeaderAccount() {
         <div className="header-account-menu" role="menu">
           <p className="header-account-name">Signed in as <strong>{name}</strong></p>
           <Link to="/study/account" role="menuitem" className="header-account-item" onClick={() => setOpen(false)}>My Account</Link>
+          {status.adminShortcut && (
+            <Link to="/admin" role="menuitem" className="header-account-item" onClick={() => setOpen(false)}>Admin</Link>
+          )}
           <button type="button" role="menuitem" className="header-account-item" onClick={signOut}>Sign out</button>
         </div>
       )}