feat(xray/dns): align DNS settings with Xray docs + UI polish

- DNS server modal: rename expectIPs -> expectedIPs (per docs); add
  per-server tag, clientIP, serveStale, serveExpiredTTL, timeoutMs;
  flip skipFallback default to false; hydration still accepts legacy
  expectIPs for back-compat.
- DNS tab: add hosts editor (domain -> IP/array), serveStale +
  serveExpiredTTL controls, "Use Preset" button bringing back the
  legacy preset gallery (Google / Cloudflare / AdGuard + Family
  variants — fixed AdGuard Family IPs that were wrong in legacy),
  and a "Delete All" button to wipe the server list at once.
- i18n: add 15 new dns.* keys across all 13 locales.
- Frontend-wide formatter pass on Vue components (whitespace and
  attribute layout only, no behavior changes).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/src/components/CustomStatistic.vue

@@ -7,8 +7,12 @@ defineProps({
 
 <template>
   <a-statistic :title="title" :value="value">
-    <template #prefix><slot name="prefix" /></template>
-    <template #suffix><slot name="suffix" /></template>
+    <template #prefix>
+      <slot name="prefix" />
+    </template>
+    <template #suffix>
+      <slot name="suffix" />
+    </template>
   </a-statistic>
 </template>