feat(admin): Add group filtering for account listings

- Add groupID parameter to ListAccounts and ListWithFilters methods
- Implement account filtering by group ID in repository query
- Add group query parameter parsing in account handler
- Update all ListAccounts/ListWithFilters call sites with groupID parameter
- Add group filter UI component to AccountTableFilters
- Add i18n translations for group filter label in English and Chinese
- Update API contract and test stubs to reflect new signature
- Enable filtering accounts by their assigned groups in admin panel

frontend/src/components/account/AccountGroupsCell.vue

@@ -41,7 +41,7 @@
         >
           <div class="mb-2 flex items-center justify-between">
             <span class="text-xs font-medium text-gray-500 dark:text-gray-400">
-              {{ t('admin.accounts.allGroups', { count: groups.length }) }}
+              {{ t('admin.accounts.groupCountTotal', { count: groups.length }) }}
             </span>
             <button
               @click="showPopover = false"