feat(theme): add top placement for sections

- Add `placement: top|bottom` to the section frontmatter
- Override `DocContent` to render hoisted bands under the page title
- Derive the zebra stripe from list position so split bands stay continuous
- Opt marketing bands out of doc typography with `rp-not-doc`
- Point the legal and privacy contact address at legal@onixbyte.com
- Condense the products pages' body copy into their section frontmatter

pnpm-lock.yaml

@@ -173,6 +173,9 @@ importers:
       '@eslint/js':
         specifier: ^9.39.4
         version: 9.39.4
+      '@mdx-js/react':
+        specifier: 3.1.1
+        version: 3.1.1(@types/react@19.2.14)(react@19.2.6)
       '@rspress/plugin-sitemap':
         specifier: 2.0.11
         version: 2.0.11(@rspress/core@2.0.11(@rspack/core@2.0.3(@swc/helpers@0.5.21))(@types/mdast@4.0.4)(@types/react@19.2.14)(micromark-util-types@2.0.2)(micromark@4.0.2(supports-color@7.2.0))(supports-color@7.2.0))