Replace the native browser confirm() dialog in SoraAdminView with the
project's ConfirmDialog component for UI consistency.
Changes:
- Import ConfirmDialog component
- Add confirm dialog state management (showConfirmDialog, confirmDialogMessage, pendingClearUserId)
- Replace clearUserStorage() with confirmClearStorage() and handleConfirmClear()
- Add ConfirmDialog to template with danger styling
- Create SoraAdminView with overview, user stats, and generations tabs
- Add /admin/sora route for Sora management
- Add i18n support (zh/en) for Sora admin page
- Extract Prometheus metrics to prommetrics package to avoid import cycles
- Integrate SetDBConnections/SetRedisConnections in OpsMetricsCollector