docs: fix broken GitHub code-reference blocks after fumadocs migration (#12213)

# Which Problems Are Solved

Pages in `apps/docs` that embed source from GitHub via the Docusaurus
convention

````
```js reference

https://github.com/zitadel/actions/blob/main/examples/org_metadata_claim.js
```
````

stopped working after the migration from Docusaurus to fumadocs. The old
`docusaurus-theme-github-codeblock` plugin used to fetch the file and
render it; fumadocs has no support for that meta, so the page rendered
the raw URL as plain code-block text. Visible at
`/docs/apis/actions/code-examples` and 16 other pages.

# How the Problems Are Solved

- Converted every ```` ```<lang> reference\n<URL>\n``` ```` block (46
total across 17 `.mdx` files) to the native fumadocs JSX form:
`<GithubCodeBlock url="<URL>" />`. The existing `<details>`/`<summary>`
collapsibles around blocks are kept — they're an authoring choice, not
part of the rendering bug.
- Updated `apps/docs/components/github-code-block.tsx` to render via
`DynamicCodeBlock` from `fumadocs-ui/components/dynamic-codeblock`
(proper shiki highlighting) instead of raw `CodeBlock` + `Pre` (which
produced unhighlighted output). Also fixed language detection so a URL
hash like `#L10-L20` no longer pollutes the language token.
- Registered `GithubCodeBlock` globally in
`apps/docs/mdx-components.tsx`, matching how every other shared
component (`APIPage`, `Callout`, `Tab/Tabs`, `Step/Steps`, `Admonition`,
`TerminologyUpdate`) is exposed. MDX files no longer need a local
`import`.

# Additional Changes

- Normalized the two MDX files that were already using the JSX form
(`examples/secure-api/python-django.mdx`,
`examples/secure-api/java-spring.mdx`): removed their now-redundant
local `import { GithubCodeBlock }` and rewrote 9 long-form
`<GithubCodeBlock url="..."></GithubCodeBlock>` tags to self-closing for
consistency.

# Additional Context

Verified locally with `pnpm --filter @zitadel/docs dev`:

- `/docs/apis/actions/code-examples` — 20 shiki-highlighted code blocks
rendered inside the `<details>` collapsibles (was 0).
- `/docs/apis/openidoauth/claims` — line-range hashes (`#L9-L11`)
honored.
- `/docs/examples/login/flutter` — mixed languages (xml/dart/html)
detected and highlighted.
- `/docs/guides/integrate/external-audit-log` — edge case of fenced
reference indented inside a numbered list also converted and rendered.

Greps:
- `^[ \t]*\`\`\`[a-zA-Z0-9]+ reference` in `apps/docs/content/**/*.mdx`
→ 0 matches.
- `<GithubCodeBlock url="` in `apps/docs/content/**/*.mdx` → 55 matches.
- `from '@/components/github-code-block'` in
`apps/docs/content/**/*.mdx` → 0 matches.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude Opus 4.7 (1M context) <[email protected]>

apps/docs/content/examples/secure-api/python-django.mdx

@@ -8,7 +8,6 @@ import AppJWT from '../imports/_app_jwt.mdx';
 import ServiceAccountJWT from '../imports/_serviceaccount_jwt.mdx';
 import ServiceAccountRole from '../imports/_serviceaccount_role.mdx';
 import SetupPython from '../imports/_setup_python.mdx';
-import { GithubCodeBlock } from '@/components/github-code-block';
 
 This integration guide demonstrates the recommended way to incorporate ZITADEL into your Django Python application.
 It explains how to check the token validity in the API and how to check for permissions.
@@ -63,7 +62,7 @@ For this example we need the following dependencies:
 
 For the dependencies we need a requirements.txt-file with the following content:
 
-<GithubCodeBlock url="https://github.com/zitadel/example-python-django-oauth/blob/main/requirements.txt"></GithubCodeBlock>
+<GithubCodeBlock url="https://github.com/zitadel/example-python-django-oauth/blob/main/requirements.txt" />
 
 Then install all dependencies with:
 ```bash
@@ -81,7 +80,7 @@ django-admin startproject myapi .
 
 There is info needed for the introspection calls, which we put into the settings.py:
 
-<GithubCodeBlock url="https://github.com/zitadel/example-python-django-oauth/blob/main/myapi/settings.py#L125-L133"></GithubCodeBlock>
+<GithubCodeBlock url="https://github.com/zitadel/example-python-django-oauth/blob/main/myapi/settings.py#L125-L133" />
 
 and create a ".env"-file in the root folder with the settings as an example:
 ```bash
@@ -103,16 +102,16 @@ API_PRIVATE_KEY_FILE_PATH = '/tmp/example/250719519163548112.json'
 To validate the tokens, we need a validator which can be called in the event of API-calls.
 
 validator.py:
-<GithubCodeBlock url="https://github.com/zitadel/example-python-django-oauth/blob/main/myapi/validator.py"></GithubCodeBlock>
+<GithubCodeBlock url="https://github.com/zitadel/example-python-django-oauth/blob/main/myapi/validator.py" />
 
 ### Requests and URLs
 
 We define 3 different endpoints which differ in terms of requirements.
 views.py:
-<GithubCodeBlock url="https://github.com/zitadel/example-python-django-oauth/blob/main/myapi/views.py"></GithubCodeBlock>
+<GithubCodeBlock url="https://github.com/zitadel/example-python-django-oauth/blob/main/myapi/views.py" />
 
 To handle endpoints the urls have to be added to the urls.py:
-<GithubCodeBlock url="https://github.com/zitadel/example-python-django-oauth/blob/main/myapi/urls.py"></GithubCodeBlock>
+<GithubCodeBlock url="https://github.com/zitadel/example-python-django-oauth/blob/main/myapi/urls.py" />
 
 ### DB