Give MRZ license index MRZ-specific SEO metadata #74

Copilot review finding on PR #69: #69 (comment)

mrz-scanner/license/index.md has Barcode Reader title, keywords, and description. Search results and link previews can therefore label the MRZ Scanner license section as Barcode Reader.

Update the MRZ index frontmatter title, keywords, and description to describe MRZ Scanner licensing, keeping the page path and navigation intact. Content follow-up outside PR #69.