feat: 实现前端卡密管理界面

- 卡密列表展示与分页功能

- 单个/批量创建卡密

- 卡密删除与批量删除

- 卡密导出功能 (file-saver)

- 启用/禁用状态切换

- 状态判断 (有效/已使用/已失效)

- Toast 通知系统 (vue-sonner)

- 登录页面错误提示优化

- 后端登录错误消息中文化

frontend/src/components/ui/pagination/PaginationEllipsis.vue

@@ -0,0 +1,25 @@
+<script setup lang="ts">
+import type { PaginationEllipsisProps } from "reka-ui"
+import type { HTMLAttributes } from "vue"
+import { reactiveOmit } from "@vueuse/core"
+import { MoreHorizontal } from "lucide-vue-next"
+import { PaginationEllipsis } from "reka-ui"
+import { cn } from "@/lib/utils"
+
+const props = defineProps<PaginationEllipsisProps & { class?: HTMLAttributes["class"] }>()
+
+const delegatedProps = reactiveOmit(props, "class")
+</script>
+
+<template>
+  <PaginationEllipsis
+    data-slot="pagination-ellipsis"
+    v-bind="delegatedProps"
+    :class="cn('flex size-9 items-center justify-center', props.class)"
+  >
+    <slot>
+      <MoreHorizontal class="size-4" />
+      <span class="sr-only">More pages</span>
+    </slot>
+  </PaginationEllipsis>
+</template>