Initial commit: DNS Test - DNS health checking tool

Go backend (miekg/dns) + Nuxt 3 frontend (Tailwind CSS v4).

8 check categories, 52 checks total:
- Overview: @ record, WWW, MX with ASN/provider lookup
- Domain Registration: expiry, registrar (RDAP + whois fallback)
- Parent Delegation: NS records, glue, consistency
- Nameservers: 17 checks (reachability, auth, recursion, TCP/UDP, AXFR, etc.)
- SOA: serial consistency, timing values
- Mail (MX): 11 checks (CNAME, PTR, public IPs, consistency)
- Mail Auth: SPF, DKIM, DMARC
- WWW: A record, CNAME

Features:
- SSE streaming (results appear as each category completes)
- SQLite history (modernc.org/sqlite)
- Rate limiting, CORS, request logging
- Dark mode, responsive design

frontend/app/components/DomainInput.vue

@@ -0,0 +1,51 @@
+<template>
+  <form @submit.prevent="onSubmit" class="flex flex-col gap-3 sm:flex-row">
+    <div class="relative flex-1">
+      <input
+        v-model="input"
+        type="text"
+        placeholder="Enter domain name (e.g., example.com)"
+        class="w-full rounded-xl border border-gray-300 bg-white px-4 py-3 text-base shadow-sm placeholder:text-gray-400 focus:border-indigo-500 focus:outline-none focus:ring-2 focus:ring-indigo-500/20 dark:border-gray-700 dark:bg-gray-800 dark:text-white dark:placeholder:text-gray-500 dark:focus:border-indigo-400 dark:focus:ring-indigo-400/20"
+      />
+    </div>
+    <button
+      type="submit"
+      :disabled="!input.trim()"
+      class="inline-flex items-center justify-center gap-2 rounded-xl bg-indigo-600 px-6 py-3 text-base font-semibold text-white shadow-sm transition hover:bg-indigo-700 focus:outline-none focus:ring-2 focus:ring-indigo-500/20 disabled:cursor-not-allowed disabled:opacity-50 dark:bg-indigo-500 dark:hover:bg-indigo-600"
+    >
+      <svg xmlns="http://www.w3.org/2000/svg" class="h-5 w-5" fill="none" viewBox="0 0 24 24" stroke="currentColor" stroke-width="2">
+        <path stroke-linecap="round" stroke-linejoin="round" d="M21 21l-6-6m2-5a7 7 0 11-14 0 7 7 0 0114 0z" />
+      </svg>
+      Check DNS
+    </button>
+  </form>
+</template>
+
+<script setup lang="ts">
+const props = defineProps<{
+  initialValue?: string
+}>()
+
+const emit = defineEmits<{
+  submit: [domain: string]
+}>()
+
+const input = ref(props.initialValue || '')
+
+function cleanDomain(raw: string): string {
+  let domain = raw.trim()
+  domain = domain.replace(/^https?:\/\//, '')
+  domain = domain.replace(/^www\./, '')
+  domain = domain.replace(/\/+$/, '')
+  domain = domain.split('/')[0]
+  return domain.toLowerCase()
+}
+
+function onSubmit() {
+  const domain = cleanDomain(input.value)
+  if (domain) {
+    input.value = domain
+    emit('submit', domain)
+  }
+}
+</script>