Smooth screen transitions: new screen waits hidden until its data arrives, no half-built flash

- Navigator stage: the next screen mounts hidden under the current one and is revealed only when its
  first data has arrived (ScreenGate held by useAsync/useGateHold), at most 450 ms; a thin top bar shows
  after 120 ms of waiting. Push slides from the left, back from the right, tabs only fade.
- Session cache (stale-while-revalidate) for screen GETs: revisited screens draw instantly.
- Home map and stats are fetched during the splash, so the first screen arrives complete.
- Entrance pop-ins (mascot, islands, lesson cards) run on first view only, not on every revisit.
- Shop status card shows placeholders instead of a wrong «نداری» while loading.
- Re-tapping the open tab scrolls to top instead of reloading; sheets close with a swipe down.
- Quiz: «۱ از ۴» instead of «۱/۴» (read as a fraction), varied praise, «N تا پشتِ هم درست»,
  growth-mindset copy after a weak round, zero-reward tiles hidden.
- Streak: a concrete next step when the streak is 0 or today is still empty.

Checked in headless Chrome against the local backend (frame captures at 150 ms and 700 ms latency,
rapid tab tapping, full quiz run). Not checked on a real phone or iOS Safari.

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

src/screens/SupportScreen.tsx

@@ -31,7 +31,7 @@ export function SupportScreen() {
   const [sending, setSending] = useState(false);
   const [error, setError] = useState('');
   // فهرست از سرور می‌آید، پس تیکت و پاسخش با عوض شدنِ گوشی هم دیده می‌شود.
-  const tickets = useAsync(() => api.support.tickets(), []);
+  const tickets = useAsync(() => api.support.tickets(), [], { key: 'support-tickets' });
 
   async function submit() {
     if (!subject.trim() || !text.trim()) return;