统一管理后台分页样式

- 新建 AdminTablePagination 组件，统一分页 UI
- 改造 6 个前端页面使用统一分页组件：
  - 管理员管理
  - 用户管理
  - 申诉管理
  - 审计日志
  - 公告管理
  - 钱包流水
- 订单管理前后端完整改造：
  - 后端：添加 PaginatedResult 结构，支持 page/page_size 参数
  - 前端：API 支持分页参数，页面使用统一分页组件
- 所有列表页分页样式统一为商品管理的 .table-pagination 设计

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/features/admin/components/AdminTablePagination.vue

@@ -0,0 +1,67 @@
+<script setup lang="ts">
+import { computed } from 'vue'
+
+interface Props {
+  currentPage: number
+  pageSize: number
+  total: number
+  loading?: boolean
+}
+
+interface Emits {
+  (e: 'update:currentPage', value: number): void
+  (e: 'update:pageSize', value: number): void
+  (e: 'pageChange'): void
+}
+
+const props = defineProps<Props>()
+const emit = defineEmits<Emits>()
+
+const totalPages = computed(() => Math.max(1, Math.ceil(props.total / props.pageSize)))
+const currentCount = computed(() => {
+  if (!props.total) return 0
+  const start = (props.currentPage - 1) * props.pageSize
+  return Math.min(props.pageSize, props.total - start)
+})
+
+function handleSizeChange(size: number) {
+  emit('update:pageSize', size)
+  emit('update:currentPage', 1)
+  emit('pageChange')
+}
+
+function prevPage() {
+  if (props.currentPage <= 1) return
+  emit('update:currentPage', props.currentPage - 1)
+  emit('pageChange')
+}
+
+function nextPage() {
+  if (props.currentPage >= totalPages.value) return
+  emit('update:currentPage', props.currentPage + 1)
+  emit('pageChange')
+}
+</script>
+
+<template>
+  <div class="table-pagination">
+    <span class="pagination-summary">当前页 {{ currentCount }} 条，共 {{ total }} 条</span>
+    <div class="pagination-controls">
+      <span class="pagination-size-label">每页</span>
+      <el-select
+        :model-value="pageSize"
+        class="page-size-select"
+        size="small"
+        @update:model-value="handleSizeChange"
+      >
+        <el-option :value="10" label="10条" />
+        <el-option :value="20" label="20条" />
+        <el-option :value="50" label="50条" />
+        <el-option :value="100" label="100条" />
+      </el-select>
+      <span class="pagination-page">{{ currentPage }}/{{ totalPages }}页</span>
+      <el-button size="small" :disabled="currentPage <= 1 || loading" @click="prevPage">上页</el-button>
+      <el-button size="small" :disabled="currentPage >= totalPages || loading" @click="nextPage">下页</el-button>
+    </div>
+  </div>
+</template>