- Replace hardcoded MONTHS array with Intl.DateTimeFormat locale-aware monthItems useMemo
- Update budgetLabel helper to accept locale parameter and use Intl.DateTimeFormat
- Replace null loading state with PageShell + Skeleton rows
- Replace manual header with PageShell title and action prop
- Replace hardcoded 'Month'/'Year' Labels with t('budgets.month')/t('budgets.year')
- Add month/year/total keys to en.json and de.json budgets namespace