feat: scaffold Astro project with en/fr i18n routing

Sets output to static (Astro default) with path-based i18n routing
(/en/, /fr/) and no unprefixed default-locale route, per the hub
landing page design spec.

tests/routing.test.ts

@@ -0,0 +1,15 @@
+import { describe, it, expect } from 'vitest';
+import { readFileSync, existsSync } from 'node:fs';
+
+describe('locale routing', () => {
+  it('builds /en/ and /fr/ pages with correct lang attributes', () => {
+    const en = readFileSync('dist/en/index.html', 'utf-8');
+    const fr = readFileSync('dist/fr/index.html', 'utf-8');
+    expect(en).toContain('lang="en"');
+    expect(fr).toContain('lang="fr"');
+  });
+
+  it('does not build an unprefixed root page', () => {
+    expect(existsSync('dist/index.html')).toBe(false);
+  });
+});