♻️ 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-gfm-strikethrough/index.d.ts

@@ -1,19 +0,0 @@
-export {
-  gfmStrikethroughFromMarkdown,
-  gfmStrikethroughToMarkdown
-} from './lib/index.js'
-
-// Add custom data tracked to turn a syntax tree into markdown.
-declare module 'mdast-util-to-markdown' {
-  interface ConstructNameMap {
-    /**
-     * Whole strikethrough.
-     *
-     * ```markdown
-     * > | ~~a~~
-     *     ^^^^^
-     * ```
-     */
-    strikethrough: 'strikethrough'
-  }
-}