docs: fix code block styling by migrating to native fumadocs-ui components (#11646)

# Which Problems Are Solved

- Docs code blocks that display imported files (YAML configs, Go
examples) render as unstyled plain text with no syntax highlighting,
unlike fenced code blocks which go through `rehypeCode`/Shiki

# How the Problems Are Solved

- Deleted `components/docusaurus/code-block.tsx` entirely — no custom
wrapper is needed anymore
- Replaced all usages with `DynamicCodeBlock` from
`fumadocs-ui/components/dynamic-codeblock` directly in MDX files; it
handles SSR pre-rendering through the same Shiki pipeline as all other
code blocks
- Raw file content (YAML, Go) is imported as strings via webpack's
existing `asset/source` rule already configured in `next.config.mjs` —
no new infrastructure required
- In `_proxy_guide_tls_mode.mdx`, the `Commands` JSX component was
refactored from concatenated JSX array children to a single template
literal string, which is what `DynamicCodeBlock` (and any string-based
highlighter) requires
- All changes applied to both non-versioned docs and versioned snapshots
(v4.10, v4.11)

# Additional Changes

None.

# Additional Context

- Affected MDX files: YAML config files under
`self-hosting/manage/configure/`, reverse-proxy guides,
`self-hosting/deploy/compose.mdx`, and the actions
`testing-request-signature.mdx` guide

<!-- START COPILOT ORIGINAL PROMPT -->



<details>

<summary>Original prompt</summary>

> 
> ----
> 
> *This section details on the original issue you should resolve*
> 
> <issue_title>code block style is weird</issue_title>
> <issue_description>### Preflight Checklist
> 
> - [x] I could not find a solution in the existing issues, docs, nor
discussions
> - [x] I have joined the [ZITADEL chat](https://zitadel.com/chat)
> 
> ### Describe the docs your are missing or that are wrong
> 
> This hurts my eyes:
> 
> <img width="867" height="525" alt="Image"
src="https://github.com/user-attachments/assets/b7b66d92-56e1-4e0a-8dba-3cab448930fe"
/>
> 
> ### Additional Context
> 
> _No response_</issue_description>
> 
> <agent_instructions>the user reported a weirdly styled code block in
the docs page where we used to display yaml files. Investigate the docs
and fix the styling</agent_instructions>
> 
> ## Comments on the Issue (you are @copilot in this section)
> 
> <comments>
> <comment_new><author>@fforootd</author><body>
> haha, ok that is certainly weird, let me look at
that.</body></comment_new>
> </comments>
> 


</details>



<!-- START COPILOT CODING AGENT SUFFIX -->

- Fixes zitadel/zitadel#11645

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---------

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: fforootd <[email protected]>
Co-authored-by: Florian Forster <[email protected]>

apps/docs/components/docusaurus/code-block.tsx

@@ -1,14 +0,0 @@
-import React from 'react';
-
-export default function CodeBlock({ children, language, title, className, showLineNumbers: _showLineNumbers }: any) {
-  return (
-    <div className="my-4">
-      {title && <div className="bg-secondary text-secondary-foreground px-4 py-2 text-sm font-medium rounded-t-md">{title}</div>}
-      <pre className={`p-4 overflow-x-auto bg-secondary/50 rounded-b-md ${title ? 'rounded-t-none' : 'rounded-md'} ${className || ''}`}>
-        <code className={language ? `language-${language}` : ''}>
-          {children}
-        </code>
-      </pre>
-    </div>
-  );
-}