feat(11.1-04): add the Backend section, the remaining Services pages and the concept map links

- docs/backend: admin controllers, forms, lists and filters, relation
  manager, users and permissions, settings, partials and widgets, admin SPA
- docs/services: storage, outbound HTTP, realtime, Web Push, search, parity
  testing and the Frontend and AJAX (not provided) page
- Examples for cabana (with testdata/docs YAML), fetchguard, lighthouse and
  its centrifugo driver, flare, beachcomber and typesense, tide; lighthouse
  and beachcomber TestDocs* regions run on their Postgres harnesses
- concept map rows link their guide pages and the not-provided rows the
  Frontend and AJAX page; index lists Backend, Database and Services
- TestDocsRequiredPages asserts the D-08 section order

modules/tide/testdata/docs/posts-spec.yaml

@@ -0,0 +1,9 @@
+version: 1
+name: blog-posts
+description: List the posts of one blog
+steps:
+  - id: list-posts
+    route_id: GET /api/blog/posts
+    request:
+      method: GET
+      path: /api/blog/posts?page=1