feat(nav): restructure top navigation and sidebars

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.

docs/en-gb/notifications/index.md

@@ -1,10 +1,10 @@
 ---
-title: Notifications
+title: News
 ---
 
 ## Microsoft Email Delivery Issues (@outlook, @hotmail, @live, @msn and custom domain emails hosted on Microsoft)
 
-> Updated at *19 May 2026*.
+> Updated at _19 May 2026_.
 
 **Urgent Action Required for Users with Microsoft-Hosted Emails.**
 
@@ -13,7 +13,6 @@ Please be advised that our automated email service is currently experiencing sev
 To ensure uninterrupted service, please follow the guidance below based on your account status:
 
 - For Prospective Users (Before Registration): Please **do not** use a Microsoft-hosted email address to register your account. You will not receive the essential activation link. Kindly use an alternative email service provider, such as your corporate email, Gmail, etc. to complete your registration.
-- For Existing Registered Users: If your profile is currently linked to an Outlook or Hotmail address, please log in immediately and update your primary email address. You can change this by navigating to your **[User Settings -> Preferences -> Emails](https://git.onixbyte.cn/-/profile/emails)** page. Failing to do so will result in missing critical repository updates, CI/CD pipeline failure logs, and Merge Request notifications.
+- For Existing Registered Users: If your profile is currently linked to an Outlook or Hotmail address, please log in immediately and update your primary email address. You can change this by navigating to your **[User Settings -> Preferences -> Emails](https://github.com/settings/emails)** page. Failing to do so will result in missing critical repository updates, CI/CD pipeline failure logs, and Merge Request notifications.
 
 We are actively working to appeal this block with the Microsoft Postmaster Centre. We sincerely apologise for any inconvenience caused and appreciate your prompt cooperation in updating your contact details.
-