Subscription store, paywall on locked units, profile subscription bar, Tadrisino branding

- Store opens with two choices (subscription / question packs); 3- and 6-month cards
  show per-month price and saving.
- Units that need a subscription show a crown badge and open the store; a 402 from
  the quiz goes there too. «ادامه بده» skips locked units.
- Profile: subscription card with an animated days-left bar (planDurationDays).
- BrandMark (SVG) on splash, home header and footer; copyright footer; floating math
  glyphs on splash. CSS transform/opacity only; honours reduced motion.

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

src/screens/QuizScreen.tsx

@@ -95,7 +95,12 @@ export function QuizScreen({ lessonId, nodeId }: { lessonId?: number; nodeId?: s
         if (h && !h.isUnlimited && h.currentHearts <= 0) setPhase({ kind: 'noHearts', nextRefillAt: h.nextRefillAt, fullRefillAt: h.fullRefillAt });
         else setPhase({ kind: 'playing' });
       })
-      .catch((error: unknown) => alive && setPhase({ kind: 'error', error }));
+      .catch((error: unknown) => {
+        if (!alive) return;
+        // فصلِ غیرِ اول بی‌اشتراک (۴۰۲)؛ صفحه‌ی خطا معنا ندارد، کاربر یک‌راست به اشتراک‌ها می‌رود.
+        if (error instanceof ApiError && error.code === 'subscription_required') nav.replace({ name: 'subscription', view: 'subscription' });
+        else setPhase({ kind: 'error', error });
+      });
     return () => {
       alive = false;
     };