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-a-theme.api.mdx

@@ -0,0 +1,66 @@
+---
+id: create-a-theme
+title: "Create a theme"
+description: "Create a theme"
+sidebar_label: "Create a theme"
+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 a theme"}
+>
+</Heading>
+
+<MethodEndpoint
+  method={"post"}
+  path={"/api/v1/theme/"}
+  context={"endpoint"}
+>
+
+</MethodEndpoint>
+
+
+
+Create a theme
+
+<Heading
+  id={"request"}
+  as={"h2"}
+  className={"openapi-tabs__heading"}
+>
+  <Translate id="theme.openapi.request.title">Request</Translate>
+</Heading>
+
+<ParamsDetails>
+
+</ParamsDetails>
+
+<RequestSchema
+  {...require("./create-a-theme.RequestSchema.json")}
+>
+
+</RequestSchema>
+
+<StatusCodes
+  {...require("./create-a-theme.StatusCodes.json")}
+>
+
+</StatusCodes>