feat: landing analytics goals, daily bar chart, referrer tracking, contact persistence

- Add per-landing analytics goals (view/click) with admin editor toggle
- Add sticky pay button option for mobile landing pages
- Add daily purchases bar chart (created vs paid) to landing stats
- Replace single purchase count with created/paid split in stats summary
- Add referrer tracking to purchases with hostname display in stats
- Add time display to purchase cards alongside date
- Pass user timezone to stats API for correct daily grouping
- Clamp referrer (500 chars) and subid (255 chars) to backend limits
- Persist contact value per-landing-slug in localStorage
- Fire buy_success analytics goal on successful delivery
- Export USER_TIMEZONE from format utils
- Add analytics/stats translations for fa.json and zh.json locales

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/pages/PurchaseSuccess.tsx

@@ -665,6 +665,33 @@ export default function PurchaseSuccess() {
   }, [token, queryClient]);
 
   const isSuccess = purchaseStatus?.status === 'delivered';
+
+  // Fire analytics goal on successful delivery (once per purchase).
+  // Idempotency keyed by token so a page refresh doesn't double-count.
+  useEffect(() => {
+    if (!isSuccess || !token) return;
+    const FIRED_KEY = `ym_buy_success_${token}`;
+    try {
+      if (localStorage.getItem(FIRED_KEY)) return;
+    } catch {
+      /* ignore */
+    }
+    try {
+      const counterId = localStorage.getItem('ym_counter_id');
+      const w = window as unknown as Record<string, unknown>;
+      if (counterId && typeof w.ym === 'function') {
+        (w.ym as (...args: unknown[]) => void)(Number(counterId), 'reachGoal', 'buy_success');
+        try {
+          localStorage.setItem(FIRED_KEY, '1');
+        } catch {
+          /* ignore */
+        }
+      }
+    } catch {
+      /* analytics error */
+    }
+  }, [isSuccess, token]);
+
   const isPendingActivation = purchaseStatus?.status === 'pending_activation';
   const isFailed = purchaseStatus?.status === 'failed' || purchaseStatus?.status === 'expired';