devlog: Dynamic OG image generation with @ewanc26/og

Each devlog post now generates its own OpenGraph image on demand at /og. OG images are served as PNG with 24-hour cache headers, generated using @ewanc26/og with the devlog colour palette (warm amber #e2a93b on dark #1a1816).

Each post page now injects:

• og:image — the generated image URL
• og:type — article
• twitter:card — summary_large_image
• twitter:image — the generated image URL

Endpoint: GET /og?title=<title>&description=<description>

Built with @ewanc26/og, which uses Satori for JSX-to-SVG and resvg-js for SVG-to-PNG rendering.

Part of the @ewanc26/pkgs monorepo.