Enable .com domain import from vertices.txt.gz

Filter imported domains to only .com TLD for now.
Re-enabled the import loop that was disabled for testing.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

domain.go

@@ -241,7 +241,11 @@ func (c *Crawler) ImportDomainsInBackground(filename string) {
 					reverseHostName := strings.TrimSpace(parts[1])
 					if reverseHostName != "" {
 						host := normalizeHost(reverseHost(reverseHostName))
-						domains = append(domains, domainEntry{host: host, tld: getTLD(host)})
+						tld := getTLD(host)
+						// Only import .com domains for now
+						if tld == "com" {
+							domains = append(domains, domainEntry{host: host, tld: tld})
+						}
 					}
 				}
 			}