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/extensions/security.md

@@ -0,0 +1,35 @@
+---
+title: Security
+sidebar_position: 9
+---
+
+<!--
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements.  See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership.  The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License.  You may obtain a copy of the License at
+
+  http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied.  See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+
+# Security
+
+By default, extensions are disabled and must be explicitly enabled by setting the `ENABLE_EXTENSIONS` feature flag. Built-in extensions are included as part of the Superset codebase and are held to the same security standards and review processes as the rest of the application.
+
+For external extensions, administrators are responsible for evaluating and verifying the security of any extensions they choose to install, just as they would when installing third-party NPM or PyPI packages. At this stage, all extensions run in the same context as the host application, without additional sandboxing. This means that external extensions can impact the security and performance of a Superset environment in the same way as any other installed dependency.
+
+We plan to introduce an optional sandboxed execution model for extensions in the future (as part of an additional SIP). Until then, administrators should exercise caution and follow best practices when selecting and deploying third-party extensions. A directory of community extensions is available in the [Community Extensions](./registry.md) page. Note that these extensions are not vetted by the Apache Superset project—administrators must evaluate each extension before installation.
+
+**Any performance or security vulnerabilities introduced by external extensions should be reported directly to the extension author, not as Superset vulnerabilities.**
+
+Any security concerns regarding built-in extensions (included in Superset's monorepo) should be reported to the Superset Security mailing list for triage and resolution by maintainers.