feat: scaffold Astro project with layout, nav, hero and concept sections

- Add global ocean-themed styles (Inter + Sora, glassmorphism utilities).
- Wire up base layout, sticky nav and footer respecting base path.
- Build hero with stylised rock SVG + sonar ambient rings and concept pipeline schematic.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

astro.config.mjs

@@ -0,0 +1,18 @@
+import { defineConfig } from 'astro/config';
+import tailwind from '@astrojs/tailwind';
+
+export default defineConfig({
+  site: 'https://laboratoire.freeboxos.fr',
+  base: '/nowyousea/',
+  output: 'static',
+  trailingSlash: 'ignore',
+  integrations: [tailwind({ applyBaseStyles: false })],
+  build: {
+    inlineStylesheets: 'auto',
+  },
+  vite: {
+    build: {
+      cssCodeSplit: true,
+    },
+  },
+});