Add import-in-astro.sh for importing Maven site output into Astro

Add import-in-astro.sh for importing Maven site output into Astro

Replaces import-in-hugo.sh for the new Astro-based website. Key
differences vs. the Hugo version:
- Content → src/content/projects/PROJECT/VERSION/ (HTML + YAML frontmatter)
- Routing → src/pages/PROJECT/ (current) or src/pages/projects/P/V/ (archived)
- Static  → public/projects/PROJECT/VERSION/
- No Hugo shortcode transformation for <pre> blocks
- Relative generated-doc dir links (apidocs/, xref/ etc.) are rewritten
  to absolute /projects/X/Y/DIR/index.html URLs, because these dirs always
  live under /projects/ regardless of whether the content page is served
  from the visible (/<project>/) or archived (/projects/X/Y/) URL

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>