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/mdast-util-to-markdown/lib/util/check-strong.js

@@ -0,0 +1,21 @@
+/**
+ * @import {Options, State} from 'mdast-util-to-markdown'
+ */
+
+/**
+ * @param {State} state
+ * @returns {Exclude<Options['strong'], null | undefined>}
+ */
+export function checkStrong(state) {
+  const marker = state.options.strong || '*'
+
+  if (marker !== '*' && marker !== '_') {
+    throw new Error(
+      'Cannot serialize strong with `' +
+        marker +
+        '` for `options.strong`, expected `*`, or `_`'
+    )
+  }
+
+  return marker
+}