docs: docusaurus setup (#3541)

# What does this PR do?

- Docusaurus server setup
- Deprecates Sphinx build pipeline
- Deprecates remaining references to Readthedocs
- MDX compile errors and broken links to be addressed in follow-up PRs

<!-- Provide a short summary of what this PR does and why. Link to relevant issues if applicable. -->

<!-- If resolving an issue, uncomment and update the line below -->

<!-- Closes #[issue-number] -->

## Test Plan

```
npm install
npm gen-api-docs all
npm run build
```

<!-- Describe the tests you ran to verify your changes with result summaries. *Provide clear instructions so the plan can be easily re-executed.* -->

docs/package.json

@@ -0,0 +1,44 @@
+{
+  "name": "docusaurus-template-openapi-docs",
+  "version": "4.3.7",
+  "private": true,
+  "scripts": {
+    "docusaurus": "docusaurus",
+    "start": "docusaurus start",
+    "build": "docusaurus build",
+    "swizzle": "docusaurus swizzle",
+    "deploy": "docusaurus deploy",
+    "clear": "docusaurus clear",
+    "serve": "docusaurus serve",
+    "write-translations": "docusaurus write-translations",
+    "write-heading-ids": "docusaurus write-heading-ids",
+    "gen-api-docs": "docusaurus gen-api-docs",
+    "clean-api-docs": "docusaurus clean-api-docs",
+    "gen-api-docs:version": "docusaurus gen-api-docs:version",
+    "clean-api-docs:version": "docusaurus clean-api-docs:version"
+  },
+  "dependencies": {
+    "@docusaurus/core": "3.8.1",
+    "@docusaurus/preset-classic": "3.8.1",
+    "@easyops-cn/docusaurus-search-local": "^0.52.1",
+    "@mdx-js/react": "^3.0.0",
+    "clsx": "^2.0.0",
+    "docusaurus-plugin-openapi-docs": "4.3.7",
+    "docusaurus-theme-openapi-docs": "4.3.7",
+    "prism-react-renderer": "^2.3.0",
+    "react": "^19.0.0",
+    "react-dom": "^19.0.0"
+  },
+  "browserslist": {
+    "production": [
+      ">0.5%",
+      "not dead",
+      "not op_mini all"
+    ],
+    "development": [
+      "last 1 chrome version",
+      "last 1 firefox version",
+      "last 1 safari version"
+    ]
+  }
+}