chore: update sidenav with new sections and entries

Wires up all the new pages added in the previous commits:

- New top-level "PAGES" section: Profile, Settings, Invoice, Pricing,
  FAQ, Calendar, Kanban, Chat, File Manager, Projects, and an Error
  submenu (404 / 500 / Maintenance)
- New top-level "Mailbox" section: Inbox, Read Message, Compose
- Tables section now includes Data Tables alongside Simple Tables
- Forms section replaced with the four new entries: Elements, Layout,
  Validation, Wizard (drops the old General Elements link)
- Documentation section gains a "Recommended Integrations" entry next
  to Color Mode, with a bi-puzzle icon