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

- Snapshot all four versioned docs sections at v6.1.0; master continues to
  serve as "Next" (lastVersion: current, banner: unreleased) so editing
  master keeps updating the canonical URLs
- Enable the previously-disabled components plugin and version it
- Rename stale "developer_portal" references to "developer_docs" across
  package.json scripts, manage-versions.mjs, theme files (DocVersionBadge,
  DocVersionBanner), DOCS_CLAUDE.md, and README.md (URL backward-compat
  redirect /developer_portal/* preserved)
- Add admin_docs version scripts; drop dead "tutorials" plugin id from
  the version badge
- Generalize fixVersionedImports in manage-versions.mjs to walk every
  section's snapshot and rewrite ../../src/ and ../../data/ imports,
  catching admin_docs and components files that previous version cuts
  would have broken
- Remove orphan files: developer_portal_versions.json,
  tutorials_versions.json, and stray empty versions.json files inside
  components/ and developer_docs/ content directories

docs/developer_docs_versioned_docs/version-6.1.0/sidebars.js

@@ -0,0 +1,84 @@
+/**
+ * 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.
+ */
+
+module.exports = {
+  developerPortalSidebar: [
+    'index',
+    {
+      type: 'category',
+      label: 'Contributing',
+      collapsed: true,
+      items: [
+        'contributing/overview',
+        'guidelines/design-guidelines',
+        'guidelines/frontend-style-guidelines',
+        'guidelines/backend-style-guidelines',
+      ],
+    },
+    {
+      type: 'category',
+      label: 'Extensions',
+      collapsed: true,
+      items: [
+        'extensions/overview',
+        'extensions/quick-start',
+        'extensions/architecture',
+        'extensions/dependencies',
+        'extensions/contribution-types',
+        {
+          type: 'category',
+          label: 'Extension Points',
+          collapsed: true,
+          items: [
+            'extensions/extension-points/sqllab',
+          ],
+        },
+        'extensions/development',
+        'extensions/deployment',
+        'extensions/mcp',
+        'extensions/security',
+        'extensions/tasks',
+        'extensions/registry',
+      ],
+    },
+    {
+      type: 'category',
+      label: 'Testing',
+      collapsed: true,
+      items: [
+        'testing/overview',
+      ],
+    },
+    {
+      type: 'category',
+      label: 'UI Components',
+      collapsed: true,
+      link: {
+        type: 'doc',
+        id: 'components/index',
+      },
+      items: [
+        {
+          type: 'autogenerated',
+          dirName: 'components',
+        },
+      ],
+    },
+  ],
+};