feat: Migrate Astro to root - Replace Next.js completely

- Removed Next.js project (src, app, components, etc.)
- Moved Astro from dealplustech-astro/ to root
- Updated Dockerfile for Astro root deployment
- All PDPA compliance features preserved:
  * Cookie consent banner
  * Consent logging API with SQLite
  * Admin dashboard (/admin/consent-logs)
  * Privacy Policy (Thai, PDPA-compliant)
  * Terms & Conditions (Thai)
- 15 pages: homepage, 6 products, 3 blog posts, legal pages, admin
- Build: 660ms, all pages generated successfully

astro.config.mjs

@@ -0,0 +1,11 @@
+// @ts-check
+import { defineConfig } from 'astro/config';
+
+import tailwindcss from '@tailwindcss/vite';
+
+// https://astro.build/config
+export default defineConfig({
+  vite: {
+    plugins: [tailwindcss()]
+  }
+});