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/composables/useDnsCheck.ts

@@ -0,0 +1,106 @@
+import type { DnsReport, Category, Summary } from '~/types/dns'
+
+interface StreamEvent {
+  domain: string
+  category: Category
+  done?: boolean
+}
+
+export function useDnsCheck() {
+  const config = useRuntimeConfig()
+  const report = ref<DnsReport | null>(null)
+  const loading = ref(false)
+  const error = ref<string | null>(null)
+  const progress = ref(0)
+  const totalCategories = 8
+
+  async function checkDomain(domain: string) {
+    loading.value = true
+    error.value = null
+    report.value = null
+    progress.value = 0
+
+    // Initialize empty report
+    const startTime = Date.now()
+    const partialReport: DnsReport = {
+      domain,
+      timestamp: new Date().toISOString(),
+      duration_ms: 0,
+      summary: { pass: 0, warn: 0, fail: 0, info: 0 },
+      categories: [],
+    }
+
+    try {
+      const url = `${config.public.apiBase}/check/stream?domain=${encodeURIComponent(domain)}`
+      const eventSource = new EventSource(url)
+
+      await new Promise<void>((resolve, reject) => {
+        const timeout = setTimeout(() => {
+          eventSource.close()
+          reject(new Error('Request timed out after 30 seconds'))
+        }, 30000)
+
+        eventSource.onmessage = (event) => {
+          try {
+            const data = JSON.parse(event.data) as StreamEvent & { done?: boolean }
+
+            if (data.done) {
+              clearTimeout(timeout)
+              eventSource.close()
+              partialReport.duration_ms = Date.now() - startTime
+              resolve()
+              return
+            }
+
+            if (data.category) {
+              partialReport.categories.push(data.category)
+              progress.value = partialReport.categories.length
+
+              // Recalculate summary
+              const summary: Summary = { pass: 0, warn: 0, fail: 0, info: 0 }
+              for (const cat of partialReport.categories) {
+                for (const check of cat.checks) {
+                  summary[check.status]++
+                }
+              }
+              partialReport.summary = summary
+              partialReport.duration_ms = Date.now() - startTime
+
+              // Update reactively
+              report.value = { ...partialReport, categories: [...partialReport.categories] }
+            }
+          } catch {
+            // ignore parse errors
+          }
+        }
+
+        eventSource.onerror = () => {
+          clearTimeout(timeout)
+          eventSource.close()
+          if (partialReport.categories.length > 0) {
+            // Got some results, show them
+            partialReport.duration_ms = Date.now() - startTime
+            report.value = { ...partialReport }
+            resolve()
+          } else {
+            reject(new Error('Connection to DNS check server failed'))
+          }
+        }
+      })
+    } catch (e: any) {
+      // Fallback to non-streaming API
+      try {
+        const data = await $fetch<DnsReport>(`${config.public.apiBase}/check?domain=${encodeURIComponent(domain)}`)
+        report.value = data
+        progress.value = totalCategories
+      } catch (e2: any) {
+        error.value = e2.data?.error || e2.message || e.message || 'Failed to check domain'
+      }
+    } finally {
+      loading.value = false
+      progress.value = totalCategories
+    }
+  }
+
+  return { report, loading, error, progress, totalCategories, checkDomain }
+}