Backup, Update, Modules, and global Settings controllers (mail config,
PDF config, disk management, global settings) are application-wide features
not scoped to a company. Move them from Admin/ to SuperAdmin/ to match the
v3.0 UI structure where these live under Administration.
Company-scoped settings controllers remain in Admin/Settings/.
- Add Administration sidebar section (super-admin only) with Companies, Users, and Global Settings pages
- Add super-admin middleware, controllers, and API routes under /api/v1/super-admin/
- Allow super-admins to manage all companies and users across tenants
- Add user impersonation with short-lived tokens, audit logging, and UI banner
- Move system-level settings (Mail, PDF, Backup, Update, File Disk) from per-company to Administration > Global Settings
- Convert save_pdf_to_disk from CompanySetting to global Setting
- Add per-company mail configuration overrides (optional, falls back to global)
- Add CompanyMailConfigService to apply company mail config before sending emails
