i18n(frontend): translate every remaining English string on the index page

Closes the index page's i18n coverage. Combined with the page-chrome
commit, every label users see on the dashboard is now sourced from
the TOML translation files.

Per file:
- IndexPage.vue: loading-spinner tip (initial + dynamic).
- BackupModal.vue: modal title, both list-item titles + descriptions
  ("Back up" / "Restore"), in-flight busy tips ("Importing database…"
  / "Restarting panel…").
- PanelUpdateModal.vue: modal title, update-available alert,
  current/latest version row labels, "Up to date" tag + label,
  primary action button. Modal.confirm now uses the translated
  panelUpdateDialog / panelUpdateDialogDesc with #version#
  substitution; success toast uses panelUpdateStartedPopover.
- LogModal.vue: title slot ("Logs"). The Debug/Info/Notice/Warning/
  Error log-level options stay literal — they're xray's wire values,
  not user-facing labels (matches the existing settings-page choice).
- XrayLogModal.vue: title + Filter label. Direct/Blocked/Proxy stay
  literal for the same reason.
- VersionModal.vue: modal title + xray-switch alert + per-file
  tooltip + "Update all" button + custom-geo collapse header. The
  Modal.confirm flows for switchXrayVersion + updateGeofile use
  translated dialog/desc with #version# / #filename# substitution.
- CpuHistoryModal.vue: title slot.
- CustomGeoSection.vue: routing-hint alert, Add / Update-all buttons,
  every column title (computed for live locale), copy/edit/download/
  delete tooltips, copy toast, delete-confirm modal, empty-state
  text.
- CustomGeoFormModal.vue: add/edit titles, OK/cancel labels, Type/
  Alias/URL field labels, alias placeholder, all three validation
  toasts.

Total: ~50 strings localised across 8 index-page files. The Hello /
Welcome login headline cycle and a handful of literal xray wire
values (Direct/Blocked/Proxy/log levels) are intentionally kept
hardcoded.

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

frontend/src/pages/index/CustomGeoFormModal.vue

@@ -1,8 +1,11 @@
 <script setup>
 import { reactive, ref, watch } from 'vue';
+import { useI18n } from 'vue-i18n';
 import { message } from 'ant-design-vue';
 import { HttpUtil } from '@/utils';
 
+const { t } = useI18n();
+
 const props = defineProps({
   open: { type: Boolean, default: false },
   // Populate with the record when editing; null/undefined when adding.
@@ -41,22 +44,22 @@ function close() {
 function validate() {
   // Backend expects a filesystem-safe alias; legacy enforces the same regex.
   if (!/^[a-z0-9_-]+$/.test(form.alias || '')) {
-    message.error('Alias must contain only lowercase letters, digits, dashes or underscores.');
+    message.error(t('pages.index.customGeoValidationAlias'));
     return false;
   }
   const u = (form.url || '').trim();
   if (!/^https?:\/\//i.test(u)) {
-    message.error('URL must start with http:// or https://');
+    message.error(t('pages.index.customGeoValidationUrl'));
     return false;
   }
   try {
     const parsed = new URL(u);
     if (parsed.protocol !== 'http:' && parsed.protocol !== 'https:') {
-      message.error('URL must start with http:// or https://');
+      message.error(t('pages.index.customGeoValidationUrl'));
       return false;
     }
   } catch (_e) {
-    message.error('URL must start with http:// or https://');
+    message.error(t('pages.index.customGeoValidationUrl'));
     return false;
   }
   return true;
@@ -83,28 +86,28 @@ async function submit() {
 <template>
   <a-modal
     :open="open"
-    :title="editing ? 'Edit custom geo entry' : 'Add custom geo entry'"
+    :title="editing ? t('pages.index.customGeoModalEdit') : t('pages.index.customGeoModalAdd')"
     :confirm-loading="saving"
-    ok-text="Save"
-    cancel-text="Close"
+    :ok-text="t('pages.index.customGeoModalSave')"
+    :cancel-text="t('close')"
     @ok="submit"
     @cancel="close"
   >
     <a-form layout="vertical">
-      <a-form-item label="Type">
+      <a-form-item :label="t('pages.index.customGeoType')">
         <a-select v-model:value="form.type" :disabled="editing">
           <a-select-option value="geosite">geosite</a-select-option>
           <a-select-option value="geoip">geoip</a-select-option>
         </a-select>
       </a-form-item>
-      <a-form-item label="Alias">
+      <a-form-item :label="t('pages.index.customGeoAlias')">
         <a-input
           v-model:value="form.alias"
           :disabled="editing"
-          placeholder="lowercase letters, digits, dashes, underscores"
+          :placeholder="t('pages.index.customGeoAliasPlaceholder')"
         />
       </a-form-item>
-      <a-form-item label="URL">
+      <a-form-item :label="t('pages.index.customGeoUrl')">
         <a-input v-model:value="form.url" placeholder="https://" />
       </a-form-item>
     </a-form>