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.

app/Models/Site.php

@@ -0,0 +1,23 @@
+<?php
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\HasMany;
+
+class Site extends Model
+{
+    protected $fillable = [
+        'collection',
+        'domain',
+        'url',
+        'title',
+        'description',
+        'keywords',
+    ];
+
+    public function pages(): HasMany
+    {
+        return $this->hasMany(SitePage::class);
+    }
+}