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/api/schemas/slice.schema.mdx

@@ -0,0 +1,31 @@
+---
+id: slice
+title: "Slice"
+description: ""
+sidebar_label: "Slice"
+hide_title: true
+hide_table_of_contents: true
+schema: true
+sample: {"cache_timeout":0,"certification_details":"string","certified_by":"string","changed_on":"2024-07-29T15:51:28.071Z","changed_on_humanized":"string","datasource":"string","description":"string","description_markeddown":"string","edit_url":"string","form_data":{},"is_managed_externally":true,"modified":"string","owners":[0],"query_context":{},"slice_id":0,"slice_name":"string","slice_url":"string"}
+custom_edit_url: null
+---
+
+import Schema from "@theme/Schema";
+import Heading from "@theme/Heading";
+
+<Heading
+  as={"h1"}
+  className={"openapi__heading"}
+  children={"Slice"}
+>
+</Heading>
+
+
+
+
+
+<Schema
+  {...require("./slice.Schema.json")}
+>
+
+</Schema>