style: 修复前端 UI 细节问题

- 供应商/模型/统计表格增加列宽约束和 ellipsis 省略号
- 修复主题切换按钮在暗色侧边栏中不可见
- 表格添加 scroll 属性防止窄屏溢出
- 自定义表格空状态提示文案

frontend/src/pages/Providers/ModelTable.tsx

@@ -18,6 +18,7 @@ export function ModelTable({ providerId, onAdd, onEdit }: ModelTableProps) {
       title: '模型名称',
       dataIndex: 'modelName',
       key: 'modelName',
+      ellipsis: { showTitle: true },
     },
     {
       title: '状态',
@@ -70,6 +71,7 @@ export function ModelTable({ providerId, onAdd, onEdit }: ModelTableProps) {
         loading={isLoading}
         pagination={false}
         size="small"
+        locale={{ emptyText: '暂无模型，点击上方按钮添加' }}
       />
     </div>
   );

frontend/src/pages/Providers/ProviderTable.tsx

@@ -1,4 +1,4 @@
-import { Button, Table, Tag, Popconfirm, Space, Card } from 'antd';
+import { Button, Table, Tag, Popconfirm, Space, Card, Tooltip } from 'antd';
 import type { ColumnsType } from 'antd/es/table';
 import type { Provider, Model } from '@/types';
 import { ModelTable } from './ModelTable';
@@ -33,17 +33,26 @@ export function ProviderTable({
       title: '名称',
       dataIndex: 'name',
       key: 'name',
+      width: 180,
+      ellipsis: { showTitle: true },
     },
     {
       title: 'Base URL',
       dataIndex: 'baseUrl',
       key: 'baseUrl',
+      ellipsis: { showTitle: true },
     },
     {
       title: 'API Key',
       dataIndex: 'apiKey',
       key: 'apiKey',
-      render: (key: string | null | undefined) => maskApiKey(key),
+      width: 120,
+      ellipsis: { showTitle: true },
+      render: (key: string | null | undefined) => (
+        <Tooltip title={maskApiKey(key)}>
+          <span>{maskApiKey(key)}</span>
+        </Tooltip>
+      ),
     },
     {
       title: '状态',
@@ -101,6 +110,8 @@ export function ProviderTable({
           ),
         }}
         pagination={false}
+        scroll={{ x: 840 }}
+        locale={{ emptyText: '暂无供应商，点击上方按钮添加' }}
       />
     </Card>
   );

frontend/src/pages/Stats/StatsTable.tsx

@@ -40,22 +40,29 @@ export function StatsTable({
       title: '供应商',
       dataIndex: 'providerId',
       key: 'providerId',
+      width: 180,
+      ellipsis: { showTitle: true },
       render: (id: string) => providerMap.get(id) ?? id,
     },
     {
       title: '模型',
       dataIndex: 'modelName',
       key: 'modelName',
+      width: 250,
+      ellipsis: { showTitle: true },
     },
     {
       title: '日期',
       dataIndex: 'date',
       key: 'date',
+      width: 120,
     },
     {
       title: '请求数',
       dataIndex: 'requestCount',
       key: 'requestCount',
+      width: 100,
+      align: 'right',
     },
   ];
 
@@ -89,6 +96,8 @@ export function StatsTable({
         rowKey="id"
         loading={loading}
         pagination={{ pageSize: 20 }}
+        scroll={{ x: 650 }}
+        locale={{ emptyText: '暂无统计数据' }}
       />
     </Card>
   );