perf: inline CSS to drop render-blocking request

[CybotTM]

Why

Lighthouse Insights on the deployed site flagged three things on top of the 100/100/100/100 categories:

1. Render-blocking requests — assets/style.css (~110 ms LCP impact)
2. Use efficient cache lifetimes — fonts + CSS at 10 min TTL (~92 KiB savings)
3. Forced reflow 61 ms [unattributed] — not from our code; we ship zero JS

This PR fixes (1). (2) is unfixable on GitHub Pages (Pages hard-codes Cache-Control: max-age=600 for static assets and we can't override; would need Cloudflare in front). (3) is Lighthouse's own measurement layout, not us.

What

• scripts/build.py gains load_inline_css() that reads assets/style.css and rewrites url("fonts/...") → url("assets/fonts/...") so the inlined @font-face URLs resolve correctly relative to the HTML document. The rewritten URLs match the existing <link rel=preload as=font> hints, so the preload is reused for the font fetch.
• render_html() and render_index() take an inline_css argument.
• templates/base.html.j2 replaces <link rel="stylesheet" href="assets/style.css"> with <style>{{ inline_css | safe }}</style>. Font preloads stay.
• The CSS file is still copied to public/assets/style.css for direct consumers (PDF build, anyone hot-linking).

Lighthouse before vs after (local desktop preset)

Page	Before	After
/index.html	render-blocking ~110 ms	render-blocking 0 ms
/cv-executive.de.html	render-blocking ~110 ms	render-blocking 0 ms
/cv-technical.de.html	render-blocking ~110 ms	render-blocking 0 ms

All four Lighthouse categories stay at 100. Network dependency tree collapses to just the HTML document (no chained CSS request).

Trade-off

CSS is now duplicated across the three HTML files (~13 KB each, ~39 KB total). Acceptable: a CV is loaded once per visitor, the LCP win matters more than caching the same CSS across pages. The CV PDF still picks up the file from public/assets/style.css via WeasyPrint, so PDFs are unaffected.

[Copilot]

Pull request overview

This PR improves initial render performance for the generated static CV site by eliminating the render-blocking external CSS request and instead inlining the stylesheet into the HTML output, while still emitting the standalone CSS asset for non-HTML consumers (e.g., PDF generation).

Changes:

• Inline assets/style.css into rendered HTML pages via a new inline_css template variable.
• Add load_inline_css() to rewrite font URLs for correct resolution when CSS is embedded in <style>.
• Thread inline_css through render_html() / render_index() and update the base template accordingly.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
templates/base.html.j2	Replaces the external stylesheet <link> with an inlined <style> block driven by inline_css.
scripts/build.py	Loads and rewrites CSS for inlining, passes inline_css into all template renders, while continuing to copy assets/ to public/assets/.

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