fix: sync plan+tier after checkout, portal same-tab nav, cancel button always visible for paid plans, portal return URL to profile tab

frontend/src/app/dashboard/profile/page.tsx

@@ -71,7 +71,8 @@ export default function ProfilePage() {
   const [loadingPortal, setLoadingPortal] = useState(false);
   const [loadingCancel, setLoadingCancel] = useState(false);
   const [isClearing, setIsClearing] = useState(false);
-  const [activeTab, setActiveTab] = useState('account');
+  const searchParams = typeof window !== 'undefined' ? new URLSearchParams(window.location.search) : null;
+  const [activeTab, setActiveTab] = useState(searchParams?.get('tab') ?? 'account');
   const [defaultLanguage, setDefaultLanguage] = useState(settings.defaultTargetLanguage);
 
   const token = typeof window !== 'undefined' ? localStorage.getItem('token') : null;
@@ -98,7 +99,7 @@ export default function ProfilePage() {
       const res = await fetch(`${API_BASE}/api/v1/auth/billing-portal`, { headers: authHeaders });
       const j = await res.json();
       const url = j.data?.url ?? j.url;
-      if (url) window.open(url, '_blank');
+      if (url) window.location.href = url;  // same tab so return_url brings back to app
       else setStatusMsg({ type: 'err', text: t('profile.subscription.billingUnavailable') });
     } catch { setStatusMsg({ type: 'err', text: t('profile.subscription.billingError') }); }
     finally { setLoadingPortal(false); }
@@ -434,8 +435,8 @@ export default function ProfilePage() {
               </div>
             )}
 
-            {/* Danger zone */}
-            {!isFreePlan && !isCanceling && user?.stripe_subscription_id && (
+            {/* Danger zone — show if user has a paid plan (even if sub ID not yet synced) */}
+            {!isFreePlan && !isCanceling && (
               <div className="editorial-card p-10 lg:p-12 bg-white dark:bg-[#141414] border-none shadow-editorial border-l-4 border-l-red-500">
                 <div className="flex items-center gap-4 text-red-500 mb-8">
                   <ShieldAlert size={20} />