feat: initialize Astro project with Tailwind and TypeScript

- Astro 5.0 with TypeScript strict mode
- Tailwind CSS 3.4 configured with custom design system
- Project structure created (components, layouts, content, styles)
- Sitemap and RSS integrations added
- Build verified successfully

Fixes dependency conflict by using Astro 5 instead of 6

src/styles/global.css

@@ -0,0 +1,9 @@
+@tailwind base;
+@tailwind components;
+@tailwind utilities;
+
+@layer base {
+  body {
+    @apply bg-background text-text-primary font-sans;
+  }
+}