refactor: Move Astro to root, use PORT env (default 80), allow all hosts

- Move Astro files from dealplustech-astro/ to project root
- Update Dockerfile: PORT environment variable (default 80)
- Add vite.config.ts with allowedHosts: true
- Matches nixpacks behavior for Easypanel deployment
- No hardcoded ports or domains

node_modules/astro/dist/cli/info/infra/process-package-manager-user-agent-provider.js

@@ -0,0 +1,7 @@
+class ProcessPackageManagerUserAgentProvider {
+  // https://docs.npmjs.com/cli/v8/using-npm/config#user-agent
+  userAgent = process.env.npm_config_user_agent ?? null;
+}
+export {
+  ProcessPackageManagerUserAgentProvider
+};