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/BalancerFormModal.vue

@@ -95,12 +95,7 @@ const okText = computed(() =>
   <a-modal :open="open" :title="title" :ok-text="okText" :cancel-text="t('close')"
     :ok-button-props="{ disabled: !isValid }" :mask-closable="false" @ok="onOk" @cancel="close">
     <a-form :colon="false" :label-col="{ md: { span: 8 } }" :wrapper-col="{ md: { span: 14 } }">
-      <a-form-item
-        label="Tag"
-        :validate-status="tagValidateStatus"
-        :help="tagHelp"
-        has-feedback
-      >
+      <a-form-item label="Tag" :validate-status="tagValidateStatus" :help="tagHelp" has-feedback>
         <a-input v-model:value="form.tag" placeholder="unique balancer tag" />
       </a-form-item>
 
@@ -110,12 +105,7 @@ const okText = computed(() =>
         </a-select>
       </a-form-item>
 
-      <a-form-item
-        label="Selector"
-        :validate-status="selectorValidateStatus"
-        :help="selectorHelp"
-        has-feedback
-      >
+      <a-form-item label="Selector" :validate-status="selectorValidateStatus" :help="selectorHelp" has-feedback>
         <a-select v-model:value="form.selector" mode="tags" :token-separators="[',']">
           <a-select-option v-for="tag in outboundTags" :key="tag" :value="tag">{{ tag }}</a-select-option>
         </a-select>