[Docs][Util][Content] - refactor docs to single source (#919)

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Removes Platform selection, moves docs to single /content folder and no
longer gens docs. Only API docs are generated here.

<!-- RECURSEML_SUMMARY:START -->
## High-level PR Summary
This PR makes significant changes to the documentation structure by
removing platform-specific content organization and consolidating docs
into a single `/content` folder. The primary goal is to simplify the
documentation architecture by eliminating the platform-specific routing
(Next.js, React, JavaScript, Python) and instead organizing content by
topic (guides, SDK, components) regardless of platform. The PR removes
platform selection functionality, platform-specific navigation, and the
automatic generation of platform-specific documentation pages. It
introduces a new docs tree filtering system that organizes content by
section rather than by platform. These changes should make the
documentation more maintainable and easier to navigate while focusing on
the content itself rather than platform-specific variations.

⏱️ Estimated Review Time: 30-90 minutes

<details>
<summary>💡 Review Order Suggestion</summary>

| Order | File Path |
|-------|-----------|
| 1 | `docs/package.json` |
| 2 | `docs/src/lib/docs-tree.ts` |
| 3 | `docs/src/lib/navigation-utils.ts` |
| 4 | `docs/src/components/homepage/iconHover.tsx` |
| 5 | `docs/src/components/sdk/overview.tsx` |
| 6 | `docs/src/components/layouts/shared/section-utils.ts` |
| 7 | `docs/src/components/layout/custom-search-dialog.tsx` |
| 8 | `docs/src/app/api/search/route.ts` |
| 9 | `docs/src/app/docs/[[...slug]]/page.tsx` |
| 10 | `docs/src/components/layouts/docs-header-wrapper.tsx` |
| 11 | `docs/src/components/layouts/docs-layout-router.tsx` |
| 12 | `docs/src/components/layouts/docs.tsx` |
| 13 | `package.json` |
</details>



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<!-- RECURSEML_SUMMARY:END -->

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **Documentation**
* Added many new guides (auth providers, OAuth, JWT, API keys, emails,
webhooks, orgs/teams, permissions, onboarding, customization), expanded
SDK & component reference pages, examples, and navigation metadata.
* Switched docs to a simpler section-based, platform-agnostic structure
and improved getting-started and production checklists.

* **Developer Experience**
* Enhanced docs UX: improved code-example UI with platform/framework
selectors, theme-aware highlighted code blocks, image zoom, and a
centralized code-sample registry.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Co-authored-by: Konstantin Wohlwend <[email protected]>

docs/code-examples/index.ts

@@ -0,0 +1,22 @@
+import { CodeExample } from '../lib/code-examples';
+import { setupExamples } from './setup';
+
+const allExamples: Record<string, Record<string, Record<string, CodeExample[]>>> = {
+  'setup': setupExamples,
+  // Add more sections here as needed:
+  // 'auth': authExamples,
+  // 'customization': customizationExamples,
+};
+
+export function getExample(documentPath: string, exampleName: string): CodeExample[] | undefined {
+  const [section, ...rest] = documentPath.split('/');
+  const subsection = rest.join('/');
+  return allExamples[section]?.[subsection]?.[exampleName];
+}
+
+export function getDocumentExamples(documentPath: string): Record<string, CodeExample[]> | undefined {
+  const [section, ...rest] = documentPath.split('/');
+  const subsection = rest.join('/');
+  return allExamples[section]?.[subsection];
+}
+