fix: show sub-rows for single-subscription users + fix floating bar position

- Auto-expand ALL users with subscriptions (was only > 1), so users
  with single subscription also show their sub-row for selection
- FloatingActionBar: render via createPortal to document.body to
  ensure fixed positioning works correctly regardless of parent
  overflow/transform contexts (was trapped inside scrollable area)

src/pages/AdminBulkActions.tsx

@@ -1,4 +1,5 @@
 import React, { useState, useEffect, useCallback, useMemo, useRef } from 'react';
+import { createPortal } from 'react-dom';
 import { useNavigate } from 'react-router';
 import { useTranslation } from 'react-i18next';
 import {
@@ -1451,10 +1452,10 @@ export default function AdminBulkActions() {
       );
       setUsers(data.users);
       setTotal(data.total);
-      // Auto-expand all users with multiple subscriptions
+      // Auto-expand all users who have subscriptions
       const autoExpand: Record<number, boolean> = {};
       for (const u of data.users) {
-        if ((u.subscriptions?.length ?? 0) > 1) {
+        if ((u.subscriptions?.length ?? 0) > 0) {
           autoExpand[u.id] = true;
         }
       }
@@ -2181,7 +2182,8 @@ export default function AdminBulkActions() {
         </div>
       )}
 
-      {/* Floating action bar */}
+      {/* Floating action bar — portal to body for correct fixed positioning */}
+      {createPortal(
         <FloatingActionBar
           selectedUserCount={selectedUserIds.length}
           selectedSubscriptionCount={selectedSubscriptionIds.length}
@@ -2189,7 +2191,9 @@ export default function AdminBulkActions() {
           totalVisibleSubscriptionCount={allVisibleSubscriptionIds.length}
           onAction={handleOpenAction}
           onToggleAllSubscriptions={toggleAllSubscriptions}
-      />
+        />,
+        document.body,
+      )}
 
       {/* Action modal */}
       <ActionModal