refactor(frontend): comprehensive split of large view files into modular components

- Split UsersView.vue into UserCreateModal, UserEditModal, UserApiKeysModal, etc.
- Split UsageView.vue into UsageStatsCards, UsageFilters, UsageTable, etc.
- Split DashboardView.vue into UserDashboardStats, UserDashboardCharts, etc.
- Split AccountsView.vue into AccountTableActions, AccountTableFilters, etc.
- Standardized TypeScript types across new components to resolve implicit 'any' and 'never[]' errors.
- Improved overall frontend maintainability and code clarity.

frontend/src/components/admin/account/AccountBulkActionsBar.vue

@@ -0,0 +1,14 @@
+<template>
+  <div v-if="selectedIds.length > 0" class="mb-4 flex items-center justify-between p-3 bg-primary-50 rounded-lg">
+    <span class="text-sm font-medium">{{ t('admin.accounts.bulkActions.selected', { count: selectedIds.length }) }}</span>
+    <div class="flex gap-2">
+      <button @click="$emit('delete')" class="btn btn-danger btn-sm">{{ t('admin.accounts.bulkActions.delete') }}</button>
+      <button @click="$emit('edit')" class="btn btn-primary btn-sm">{{ t('admin.accounts.bulkActions.edit') }}</button>
+    </div>
+  </div>
+</template>
+
+<script setup lang="ts">
+import { useI18n } from 'vue-i18n'
+defineProps(['selectedIds']); defineEmits(['delete', 'edit']); const { t } = useI18n()
+</script>