fix(docs): correct imageZoom and {markdown_url} config in v0.12 release blog

- Use nested imageZoom.enable: true instead of scalar imageZoom: true
- Use {markdown_url} (snake_case) placeholder matching the actual template-url
  utility key, not {markdownUrl} (camelCase) which would silently not substitute

docs/content/blog/v0.12.md

@@ -43,9 +43,9 @@ hugo mod get -u github.com/imfing/hextra
 
 ![Context menu](https://github.com/user-attachments/assets/0b55bee9-6f4d-4e1d-9461-60c40208cb6c)
 
-The page context menu provides a dropdown button that lets you copy the page content as Markdown or view the raw Markdown source. As more users feed documentation into generative AI tools, having quick access to clean Markdown is increasingly useful. Custom links with template variables (`{url}`, `{title}`, `{markdownUrl}`) let you wire up "Ask AI" shortcuts or other integrations directly in the menu.
+The page context menu provides a dropdown button that lets you copy the page content as Markdown or view the raw Markdown source. As more users feed documentation into generative AI tools, having quick access to clean Markdown is increasingly useful. Custom links with template variables (`{url}`, `{title}`, `{markdown_url}`) let you wire up "Ask AI" shortcuts or other integrations directly in the menu.
 
-To use the "View as Markdown" and `{markdownUrl}` features, enable the Markdown output format in your site configuration:
+To use the "View as Markdown" and `{markdown_url}` features, enable the Markdown output format in your site configuration:
 
 ```yaml {filename="hugo.yaml"}
 outputs:
@@ -62,7 +62,7 @@ params:
       enable: true
       links:
         - name: "Ask AI"
-          url: "https://example.com?content={markdownUrl}"
+          url: "https://example.com?content={markdown_url}"
           icon: "sparkles"
 ```
 
@@ -86,7 +86,8 @@ Enable click-to-zoom on Markdown images with a new configuration option, powered
 
 ```yaml {filename="hugo.yaml"}
 params:
-  imageZoom: true
+  imageZoom:
+    enable: true
 ```
 
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