Move onboarding and support docs into the homepage flow

[johnnyhuy]

Repeated Backstage notes point to the same usability problem: important onboarding and support docs are too tucked away.

Starter scope:

• surface onboarding docs directly on the homepage
• make support and API reference easier to reach
• optimise the homepage for first-use orientation rather than only catalog navigation

Sources:

• Weekly Notes/2024 - Week 43.md
• Weekly Notes/2024 - Week 46.md
• Notes/2024-11-29 - Revamp Velo Homepage.md

Assignee: johnnyhuy