refactor: Move Astro project to root directory

- Move all Astro files from dealplustech-astro/ to root
- Archive Next.js code in _nextjs-backup/
- Update .gitignore for Astro project
- Simplify project structure

This completes the migration from Next.js to Astro.
The Astro project is now at the root level.

.next/static/chunks/app/pipe/page-e115bccb859c2d29.js

@@ -0,0 +1 @@
+(self.webpackChunk_N_E=self.webpackChunk_N_E||[]).push([[381,931,659,308,404,752,877,469],{7050:function(e,n,s){Promise.resolve().then(s.t.bind(s,8173,23)),Promise.resolve().then(s.t.bind(s,231,23))}},function(e){e.O(0,[231,173,971,23,744],function(){return e(e.s=7050)}),_N_E=e.O()}]);