chore: scaffold Astro 5 project with token/style layer

- Astro 5 static config (trailing-slash canonical, i18n en-root/no-prefixed)
- Tailwind 4 over CSS custom-property tokens (both themes via [data-theme])
- design tokens: colour/spacing/type/radius/motion per Phase 1 specs
- motion layer with reduced-motion overrides
- strict TypeScript, ESLint flat config, Prettier
- self-hosted variable fonts (Space Grotesk / Inter / JetBrains Mono)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.gitattributes

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+# Normalise line endings to LF in the repo; check out native on Windows.
+* text=auto eol=lf
+
+# Binary assets — never touch.
+*.png binary
+*.jpg binary
+*.jpeg binary
+*.webp binary
+*.avif binary
+*.pdf binary
+*.woff binary
+*.woff2 binary
+*.ico binary
+
+# Shell scripts and container files must stay LF even on Windows checkout.
+*.sh text eol=lf
+Dockerfile text eol=lf
+*.yml text eol=lf
+*.yaml text eol=lf