fix(admin): show flag for every country code, not just hardcoded 25-36

User reported the EE (Estonia) flag rendered as plain text 'EE' on the
admin servers page. Root cause: getCountryFlag() in AdminServers.tsx
and AdminServerEdit.tsx hardcoded a 25-entry codeMap that didn't
include EE; falling through to 'return code' produced raw text.

Two other admin pages (AdminRemnawaveSquadDetail, AdminUserDetail)
had bigger 35-entry maps that did include EE — so EE worked there
but MX/AR/EG/ZA and friends still wouldn't. AdminRemnawave repeated
the same 35-entry map. AdminTrafficUsage already had the correct
algorithmic ISO→regional-indicator code but as a local duplicate of
utils/subscriptionHelpers.

Unify all six on the single algorithmic helper:

- getFlagEmoji() in utils/subscriptionHelpers.ts now:
  * accepts string | null | undefined (callers don't need to guard)
  * trims whitespace
  * validates [A-Za-z]{2} before composing regional indicators
- Each admin page now either imports getFlagEmoji directly or wraps
  it with the page's preferred fallback character (e.g. '🌍' for
  empty codes where the UI expects a placeholder).

src/pages/AdminServers.tsx

@@ -20,37 +20,7 @@ const BackIcon = () => (
 );
 
 // Country flags (simple emoji mapping)
-const getCountryFlag = (code: string | null): string => {
-  if (!code) return '';
-  const codeMap: Record<string, string> = {
-    RU: '🇷🇺',
-    US: '🇺🇸',
-    DE: '🇩🇪',
-    NL: '🇳🇱',
-    GB: '🇬🇧',
-    FR: '🇫🇷',
-    FI: '🇫🇮',
-    SE: '🇸🇪',
-    PL: '🇵🇱',
-    CZ: '🇨🇿',
-    AT: '🇦🇹',
-    CH: '🇨🇭',
-    UA: '🇺🇦',
-    KZ: '🇰🇿',
-    JP: '🇯🇵',
-    KR: '🇰🇷',
-    SG: '🇸🇬',
-    HK: '🇭🇰',
-    CA: '🇨🇦',
-    AU: '🇦🇺',
-    BR: '🇧🇷',
-    IN: '🇮🇳',
-    TR: '🇹🇷',
-    IL: '🇮🇱',
-    AE: '🇦🇪',
-  };
-  return codeMap[code.toUpperCase()] || code;
-};
+import { getFlagEmoji as getCountryFlag } from '../utils/subscriptionHelpers';
 
 export default function AdminServers() {
   const { t } = useTranslation();