- Delete the blogs, opensource-projects and notifications trees
- Drop their nav entries and i18n keys
- Point the nav at the new open-source site instead
- Drop the opensource-projects sitemap priority
The old nav used bare lowercase slugs and leaned on filesystem order for
every sidebar.
- Replace the three existing nav entries with six labelled ones, keyed
through i18n.json so both locales resolve to their own text from
identical _nav.json files.
- Add _meta.json for blogs and opensource-projects, grouping entries by
topic instead of leaving them alphabetical.
- Rename the Blogs and Notifications pages so their titles match the nav
labels (Insights and News).
- Point the notification page's account-settings link at GitHub, as the
Gitea instance it referenced is retired.