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>

site/astro.config.mjs

@@ -0,0 +1,41 @@
+// @ts-check
+import { defineConfig } from 'astro/config';
+import tailwindcss from '@tailwindcss/vite';
+import { fileURLToPath } from 'node:url';
+
+// Canonical origin used for absolute URLs (sitemap, OG, hreflang, JSON-LD).
+// Overridable at build time so staging emits its own origin. See DOCKER_SPEC §3.
+const SITE = process.env.PUBLIC_SITE_URL ?? 'https://cesnimda.co.uk';
+
+const r = (p) => fileURLToPath(new URL(p, import.meta.url));
+
+// https://astro.build/config
+export default defineConfig({
+  site: SITE,
+  // ROUTING_SPEC §1: trailing-slash canonical, directory output.
+  trailingSlash: 'always',
+  build: { format: 'directory', inlineStylesheets: 'auto' },
+  // I18N_SPEC §1: en at root, no prefixed. Localised slugs are handled by explicit
+  // page files + the slug map module (ARCHITECTURE A5), not automatic locale routing.
+  i18n: {
+    defaultLocale: 'en',
+    locales: ['en', 'no'],
+    routing: { prefixDefaultLocale: false, redirectToDefaultLocale: false },
+  },
+  prefetch: false,
+  compressHTML: true,
+  vite: {
+    plugins: [tailwindcss()],
+    resolve: {
+      alias: {
+        '@': r('./src'),
+        '@i18n': r('./src/i18n'),
+        '@components': r('./src/components'),
+        '@layouts': r('./src/layouts'),
+        '@styles': r('./src/styles'),
+        '@scripts': r('./src/scripts'),
+        '@lib': r('./src/lib'),
+      },
+    },
+  },
+});