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

package.json

@@ -24,6 +24,7 @@
   },
   "devDependencies": {
     "@eslint/js": "^9.39.4",
+    "@mdx-js/react": "3.1.1",
     "@rspress/plugin-sitemap": "2.0.11",
     "@tailwindcss/postcss": "^4.3.0",
     "@types/node": "^22.8.1",