refactor: item 29 cleanup

F16 F17 F18 F19 F20 F21: import polling backs off and pauses in a hidden tab, one date format module, fake timers in the import tests, error codes instead of raw messages, one safe storage wrapper, dead code.

src/components/AccountInfoCard.jsx

@@ -3,11 +3,12 @@ import {UserRound} from 'lucide-react';
 
 import {Card, CardContent, CardHeader, CardTitle} from '@/components/ui/card';
 import {useCurrentUserContext} from '../context/CurrentUserContext.jsx';
+import {formatDateTime} from '../utils/format.js';
 
 const formatDate = (value, locale) => {
     if (!value) return '—';
     try {
-        return new Date(value).toLocaleString(locale);
+        return formatDateTime(value, locale);
     } catch {
         return value;
     }