fix: handle multi-IP and add tests for clickable IP link

Follow-up to #78:
- Use primaryIp() so href targets the first IP when data.ip is comma-separated (e.g. "192.168.1.1, 2001:db8::1")
- Add primaryIp() helper to maskIp.ts
- Add 4 tests covering single IP link, absent IP, multi-IP href, multi-IP display text

frontend/src/utils/maskIp.ts

@@ -8,3 +8,8 @@ export function maskIp(ip: string): string {
   if (parts.length === 4) return `${parts[0]}.${parts[1]}.XX.XX`
   return ip
 }
+
+export function primaryIp(ip: string): string {
+  if (!ip?.trim()) return ''
+  return ip.split(',')[0].trim()
+}