feat(ui): support /bento base path and improve storage flows

[kutaelee]

Summary

• support serving the UI under /bento by wiring basename/base-path helpers into routing and dev proxy paths
• improve files, media, breadcrumbs, upload, and admin storage flows, including related locale updates
• add the volume auto-scan playbook and extend the dev server scaffolding for storage scan behavior

Validation

• pnpm --dir /home/mining/Bento/packages/ui typecheck
• pnpm --dir /home/mining/Bento/packages/ui lint

[kutaelee]

Closing this stale failed PR to keep the public maintenance surface clear. The branch is preserved and can be reopened or superseded by a fresh, passing PR.