♻️ Restructure: Move Astro to repository root

BREAKING CHANGE: Astro project is now at repository root
- Removed dealplustech-astro subdirectory
- Moved all Astro files to root
- Updated PostCSS config to .cjs
- Removed old Next.js files

✅ 11 pages built successfully
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✅ Ready for Easypanel deployment (no root dir needed)

Migration path:
- Old structure: /dealplustech-astro/
- New structure: / (root)

dealplustech-astro/node_modules/mdast-util-to-markdown/lib/util/format-heading-as-setext.js

@@ -1,34 +0,0 @@
-/**
- * @import {State} from 'mdast-util-to-markdown'
- * @import {Heading} from 'mdast'
- */
-
-import {EXIT, visit} from 'unist-util-visit'
-import {toString} from 'mdast-util-to-string'
-
-/**
- * @param {Heading} node
- * @param {State} state
- * @returns {boolean}
- */
-export function formatHeadingAsSetext(node, state) {
-  let literalWithBreak = false
-
-  // Look for literals with a line break.
-  // Note that this also
-  visit(node, function (node) {
-    if (
-      ('value' in node && /\r?\n|\r/.test(node.value)) ||
-      node.type === 'break'
-    ) {
-      literalWithBreak = true
-      return EXIT
-    }
-  })
-
-  return Boolean(
-    (!node.depth || node.depth < 3) &&
-      toString(node) &&
-      (state.options.setext || literalWithBreak)
-  )
-}