Initial commit: Laravel scaffold + Common Crawl site indexing

Adds Site/SitePage models and the crawlindex:fetch command, which pulls
CDX index records from Common Crawl and optionally enriches them with
page title/description/keywords/body text extracted from the WARC
archive. CDX/WARC access and the site/page upsert logic live in
CommonCrawlIndexService and WarcRecordFetcher.

.gitattributes

@@ -0,0 +1,11 @@
+* text=auto eol=lf
+
+*.blade.php diff=html
+*.css diff=css
+*.html diff=html
+*.md diff=markdown
+*.php diff=php
+
+/.github export-ignore
+CHANGELOG.md export-ignore
+.styleci.yml export-ignore