docs: rename Network Routes to Routes, deprecate, and relocate Browser Client Architecture (#792)

* docs: rename Network Routes to Routes, deprecate, and relocate Browser Client Architecture

- Rename the docs sidebar entry "Network Routes" to "Routes" and the page H1
- Add a deprecation note to the Routes page: all use cases except exit nodes
  have moved to Networks; reconcile the body framing accordingly
- Move Browser Client Architecture under Peers > Browser Client
  (/manage/peers/browser-client/architecture), nest the nav, add a redirect,
  and update cross-links
- Shrink the site-to-site Architecture diagram boxes to fit their content

* docs: rename Routes nav 'Concept' link to 'Overview'

next.config.mjs

@@ -31,6 +31,11 @@ const nextConfig = {
                 destination: '/manage/networks',
                 permanent: true,
             },
+            {
+                source: '/about-netbird/browser-client-architecture',
+                destination: '/manage/peers/browser-client/architecture',
+                permanent: true,
+            },
             {
                 source: '/manage/network-routes/use-cases/by-scenario/site-to-vpn',
                 destination: '/manage/networks/use-cases/site-to-vpn',