Add MDX blog system and first post

[oosuhada]

Goal

Add a file-based /blog system to oosu.dev and publish the first technical post about automating Hanseong TFX173T monitor brightness with m1ddc, Swift, and LaunchAgent. Also tighten Cloudflare-facing production behavior found during dashboard review.

Current status

• Adds /blog, /blog/[slug], and /blog/feed.xml routes.
• Adds MDX frontmatter parsing, published-post filtering, static params, related-post lookup, SEO metadata, JSON-LD, sitemap inclusion, and RSS output.
• Adds code-block syntax highlighting with filename captions and copy buttons.
• Adds the first published MDX post at content/blog/m1ddc-monitor-brightness.mdx.
• Updates Docker runtime copy so content/ exists in the standalone image.
• Enables Cloudflare Always Use HTTPS for oosu.dev from the dashboard.
• Adds /favicon.ico handling so browser/default favicon requests no longer return 404.
• Adds cache headers for public AI docs, favicons, and tracked static image asset folders.

Changed files

• src/app/blog/**
• src/lib/blog.ts
• src/components/blog/**
• content/blog/m1ddc-monitor-brightness.mdx
• src/app/sitemap.ts
• src/lib/seo.ts
• src/app/globals.css
• Dockerfile
• package.json, pnpm-lock.yaml
• src/app/favicon.ico/route.ts
• src/app/layout.tsx
• next.config.ts

Validation commands run

• pnpm exec tsc --noEmit passed during earlier blog work.
• Changed-file ESLint passed during earlier blog work.
• /opt/homebrew/bin/corepack pnpm build passed locally after Cloudflare/favicon changes.
• Local HTTP checks passed for /favicon.ico, /favicon.svg, /llms.txt, tracked static images, and /blog.
• Mac mini Docker Compose rebuild completed with /opt/homebrew/bin/docker compose -f ops/orbstack/compose.prod.yml up -d --build app.
• Server checks passed for http://127.0.0.1:3010/favicon.ico and http://127.0.0.1:3010/blog.
• Live checks passed for http://oosu.dev redirecting to HTTPS, https://oosu.dev/favicon.ico, https://oosu.dev/favicon.svg, https://oosu.dev/blog, https://oosu.dev/llms.txt, and tracked image asset cache headers.

Notes

• Full next lint is still blocked by existing unrelated React Hooks lint findings in chat/sidebar/UI files. The changed blog files passed targeted ESLint during the blog work.
• Cloudflare Security Analytics showed no recent firewall/security events during the dashboard review; the favicon 404 was an actual small site-side missing route.

[oosuhada]

Closing this stale branch-to-branch PR because it has no CI signal and the main-facing AskOosu engineering evidence work is tracked separately in #9 with green checks. Branch is left intact for reference.