feat: scaffold Astro 7 with Tailwind 4, MDX, sitemap, node adapter and tooling

- Tailwind v4 via @tailwindcss/vite + typography plugin
- astro-icon (Tabler), self-hosted Rubik/Inter, RSS, Pagefind postbuild
- Prettier (astro + tailwind plugins), editorconfig
- new:post script with Turkish-aware slugify

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.prettierignore

@@ -0,0 +1,5 @@
+dist/
+.astro/
+node_modules/
+package-lock.json
+docs/