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/pages/xray/DnsPresetsModal.vue

@@ -0,0 +1,103 @@
+<script setup>
+import { computed } from 'vue';
+import { useI18n } from 'vue-i18n';
+
+const { t } = useI18n();
+
+const props = defineProps({
+  open: { type: Boolean, default: false },
+});
+
+const emit = defineEmits(['update:open', 'install']);
+
+const PRESETS = [
+  {
+    name: 'Google DNS',
+    family: false,
+    data: [
+      '8.8.8.8',
+      '8.8.4.4',
+      '2001:4860:4860::8888',
+      '2001:4860:4860::8844',
+    ],
+  },
+  {
+    name: 'Cloudflare DNS',
+    family: false,
+    data: [
+      '1.1.1.1',
+      '1.0.0.1',
+      '2606:4700:4700::1111',
+      '2606:4700:4700::1001',
+    ],
+  },
+  {
+    name: 'AdGuard DNS',
+    family: false,
+    data: [
+      '94.140.14.14',
+      '94.140.15.15',
+      '2a10:50c0::ad1:ff',
+      '2a10:50c0::ad2:ff',
+    ],
+  },
+  {
+    name: 'AdGuard Family DNS',
+    family: true,
+    data: [
+      '94.140.14.15',
+      '94.140.15.16',
+      '2a10:50c0::bad1:ff',
+      '2a10:50c0::bad2:ff',
+    ],
+  },
+  {
+    name: 'Cloudflare Family DNS',
+    family: true,
+    data: [
+      '1.1.1.3',
+      '1.0.0.3',
+      '2606:4700:4700::1113',
+      '2606:4700:4700::1003',
+    ],
+  },
+];
+
+const title = computed(() => t('pages.xray.dns.dnsPresetTitle'));
+
+function close() { emit('update:open', false); }
+function install(preset) {
+  emit('install', [...preset.data]);
+}
+</script>
+
+<template>
+  <a-modal :open="open" :title="title" :footer="null" :mask-closable="false" @cancel="close">
+    <a-list bordered>
+      <a-list-item v-for="preset in PRESETS" :key="preset.name" class="preset-row">
+        <a-space size="small" align="center">
+          <a-tag :color="preset.family ? 'purple' : 'green'">
+            {{ preset.family ? t('pages.xray.dns.dnsPresetFamily') : 'DNS' }}
+          </a-tag>
+          <span class="preset-name">{{ preset.name }}</span>
+        </a-space>
+        <a-button type="primary" size="small" @click="install(preset)">
+          {{ t('install') }}
+        </a-button>
+      </a-list-item>
+    </a-list>
+  </a-modal>
+</template>
+
+<style scoped>
+.preset-row {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  gap: 8px;
+}
+
+.preset-name {
+  font-weight: 500;
+}
+</style>