Generate per-page OG images

[braboj]

Summary

The same og-banner.png is used for all 36 pages. Shared links to different chapters/recipes look identical on social platforms, reducing click incentive.

Options

• Astro OG image integration (e.g., @astrojs/og or satori + sharp)
• Static generation at build time from page title + chapter name
• Template: teal background + Git icon + page title + "Code with Branko"

Acceptance criteria

• Each page has a unique OG image with its title
• Images generated at build time (no runtime dependency)
• Fallback to the existing banner if generation fails

Found by

360-degree analysis (Discovery category), 2026-04-29.