Add backlinks section to the site detail page

Shows inbound links (who links to this site, via Site::inboundLinks())
with the referring site, source page, and anchor text — paginated
separately from the Pages table via a distinct page-name query param
so both can paginate independently. Also surfaces a simple outbound
link count and a "N backlinks from M referring domains" summary.

Verified against real data: crawled podcastyradio.es (previously only
known as a backlink target from 00podcast.es) and confirmed its detail
page correctly shows that inbound link with the right anchor text.

app/Http/Controllers/SiteController.php

@@ -9,8 +9,22 @@ class SiteController extends Controller
 {
     public function show(Site $site): View
     {
-        $pages = $site->pages()->orderBy('url')->paginate(50);
+        $pages = $site->pages()->orderBy('url')->paginate(50, ['*'], 'pages_page');
 
-        return view('sites.show', ['site' => $site, 'pages' => $pages]);
+        $backlinks = $site->inboundLinks()
+            ->with(['site', 'sitePage'])
+            ->latest()
+            ->paginate(50, ['*'], 'backlinks_page');
+
+        $referringDomainsCount = $site->inboundLinks()->distinct()->count('site_id');
+        $outboundLinksCount = $site->outboundLinks()->count();
+
+        return view('sites.show', [
+            'site' => $site,
+            'pages' => $pages,
+            'backlinks' => $backlinks,
+            'referringDomainsCount' => $referringDomainsCount,
+            'outboundLinksCount' => $outboundLinksCount,
+        ]);
     }
 }