fix: improve campaign stats, shared chart components, and i18n coverage

- Extract shared chart constants to constants/charts.ts
- Add TREND_STYLES to stats/constants.ts for reuse
- Fix useChartColors with MutationObserver for theme changes
- Fix DailyChart date parsing to prevent timezone shift
- Add truncate to StatCard value for overflow safety
- Fix CampaignCard copy feedback inside try block
- Add NaN validation and staleTime to AdminCampaignStats
- Replace hardcoded strings with i18n keys in Referral page
- Add missing i18n keys across all 4 locales (en, ru, zh, fa)
- Add sales stats route to AdminPanel and App router

src/components/stats/StatCard.tsx

@@ -21,7 +21,9 @@ export function StatCard({
         {icon}
         <span>{label}</span>
       </div>
-      <div className={`mt-1 text-base font-semibold sm:text-lg ${valueClassName}`}>{value}</div>
+      <div className={`mt-1 truncate text-base font-semibold sm:text-lg ${valueClassName}`}>
+        {value}
+      </div>
     </div>
   );
 }