docs: cut 6.1.0 versions for user_docs, admin_docs, developer_docs, components

Snapshots all four versioned Docusaurus sections at v6.1.0, cut from
master after the version-cutting tooling (#39837), broken-internal-
links fix (#40102), and user_docs rename (#40171) all landed. With
the rename in place, all four sections now produce parallel-named
files at the docs/ root (no more bare `versioned_docs/` outlier).

Versioning behavior: lastVersion stays at current for every section,
so the canonical URLs (/user-docs/..., /admin-docs/...,
/developer-docs/..., /components/...) continue to render content
from master. The current version is consistently labeled "Next"
with an unreleased banner, and 6.1.0 is a historical pin accessible
only via its explicit version segment.

Component playground: previously disabled: true in versions-config.json,
now enabled and versioned.

Snapshot includes:
- All MDX content for the four sections.
- Auto-gen captured fresh: 74 database pages (engine spec metadata),
  ~1,800 API reference files (openapi.json), 59 component pages
  (Storybook stories).
- Data imports frozen at cut time into snapshot-local _versioned_data/
  dirs:
    user_docs_versioned_docs/version-6.1.0/_versioned_data/src/data/databases.json
      (canonical 80-database diagnostics from master, preserved by the
      generator's input-hash cache)
    admin_docs_versioned_docs/version-6.1.0/_versioned_data/data/countries.json
    admin_docs_versioned_docs/version-6.1.0/_versioned_data/static/feature-flags.json
    developer_docs_versioned_docs/version-6.1.0/_versioned_data/static/data/components.json
- Import paths in deeply-nested files rewritten so they still resolve
  from one directory deeper inside the snapshot.
- developer_docs/extensions/overview.md snapshot has the FIXED
  ./mcp.md form (from #40102), so the SPA-nav 404 isn't baked into
  the 6.1.0 version.

Verified via full yarn build: exit 0, no broken links surfaced by
onBrokenLinks: throw.

docs/developer_docs_versioned_docs/version-6.1.0/api/create-security-user-registrations.api.mdx

@@ -0,0 +1,66 @@
+---
+id: create-security-user-registrations
+title: "Create security user registrations"
+description: "Create security user registrations"
+sidebar_label: "Create security user registrations"
+hide_title: true
+hide_table_of_contents: true
+api: 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
+sidebar_class_name: "post api-method"
+info_path: developer-docs/api/superset
+custom_edit_url: null
+hide_send_button: true
+show_extensions: true
+---
+
+import MethodEndpoint from "@theme/ApiExplorer/MethodEndpoint";
+import ParamsDetails from "@theme/ParamsDetails";
+import RequestSchema from "@theme/RequestSchema";
+import StatusCodes from "@theme/StatusCodes";
+import OperationTabs from "@theme/OperationTabs";
+import TabItem from "@theme/TabItem";
+import Heading from "@theme/Heading";
+import Translate from "@docusaurus/Translate";
+
+<Heading
+  as={"h1"}
+  className={"openapi__heading"}
+  children={"Create security user registrations"}
+>
+</Heading>
+
+<MethodEndpoint
+  method={"post"}
+  path={"/api/v1/security/user_registrations/"}
+  context={"endpoint"}
+>
+
+</MethodEndpoint>
+
+
+
+Create security user registrations
+
+<Heading
+  id={"request"}
+  as={"h2"}
+  className={"openapi-tabs__heading"}
+>
+  <Translate id="theme.openapi.request.title">Request</Translate>
+</Heading>
+
+<ParamsDetails>
+
+</ParamsDetails>
+
+<RequestSchema
+  {...require("./create-security-user-registrations.RequestSchema.json")}
+>
+
+</RequestSchema>
+
+<StatusCodes
+  {...require("./create-security-user-registrations.StatusCodes.json")}
+>
+
+</StatusCodes>