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/TextModal.vue

@@ -39,19 +39,18 @@ function download(content, name) {
 
 <template>
   <a-modal :open="open" :title="title" :closable="true" @cancel="close">
-    <a-textarea
-      :value="content"
-      readonly
-      :auto-size="{ minRows: 10, maxRows: 20 }"
-      class="text-modal-content"
-    />
+    <a-textarea :value="content" readonly :auto-size="{ minRows: 10, maxRows: 20 }" class="text-modal-content" />
     <template #footer>
       <a-button v-if="fileName" @click="download(content, fileName)">
-        <template #icon><DownloadOutlined /></template>
+        <template #icon>
+          <DownloadOutlined />
+        </template>
         {{ fileName }}
       </a-button>
       <a-button type="primary" @click="copy(content)">
-        <template #icon><CopyOutlined /></template>
+        <template #icon>
+          <CopyOutlined />
+        </template>
         Copy
       </a-button>
     </template>