BO02 - Create a route to the BackOffice, allowed to Organizers only

[valekuro]

• Add 404 page
• Add backoffice page (visible only if organizer is true)

[github-actions[bot]]

⚡️🏠 Lighthouse report

We ran Lighthouse against the changes and produced this report. Here's the summary:

Category	Score
🟢 Performance	100
🟢 Accessibility	100
🟢 Best practices	100
🟢 SEO	100

Lighthouse ran against http://localhost:4321/