Use navigator.language instead of hardcoded en-US in Dashboard formatDate

[mighty840]

Description

The admin Dashboard's formatDate helper uses a hardcoded 'en-US' locale for toLocaleDateString(). This should respect the user's browser locale or the app's current language setting.

Files to Change

• packages/admin/src/pages/Dashboard.tsx — line 305

Steps

1. Replace 'en-US' with navigator.language or the current i18n locale
2. Verify date formatting still looks correct across common locales

Effort

XS — single line change