feat(11.1-04): add the Services section with a verified Queued jobs page

- docs/services/jobs.md: declaring, registering and dispatching jobs, the
  summer_jobs record, progress, cancellation and workers
- conga ExampleJob plus dispatch and status regions run by TestDocsDispatch
  on the package's Postgres harness (DocsApp in export_docs_test.go)
- concept map links the queued jobs row; services/jobs is a required page

docs/site.yaml

@@ -17,6 +17,8 @@ sections:
     title: Architecture
   - name: plugins
     title: Plugins
+  - name: services
+    title: Services
   - name: console
     title: Console
   - name: api