Enhance VpnConfigDto to include ClientEmail and update related components

- Added ClientEmail property to VpnConfigDto for better client identification.
- Updated ConfigCard to display the ClientEmail in the UI for improved user information.
- Modified API schema and types to accommodate the new ClientEmail field.
- Enhanced localization for displaying the ClientEmail in both Russian and English.

frontend/src/features/configs/ConfigCard.tsx

@@ -80,6 +80,9 @@ export function ConfigCard({ config }: { config: VpnConfigDto }) {
           <div className="text-sm text-muted-foreground">
             ↑ {formatBytes(config.usedUpBytes)} ↓ {formatBytes(config.usedDownBytes)}
           </div>
+          <p className="truncate font-mono text-xs text-muted-foreground/60">
+            {t('configs.panelEmail', { email: config.clientEmail })}
+          </p>
           <div className="flex flex-wrap gap-2">
             <Button size="sm" variant="outline" onClick={() => setDetailsOpen(true)}>
               <QrCode className="h-4 w-4" />