feat: 添加对话应用选择和知识库切换功能

- 新增对话应用管理模块(dify-chat-apps)，支持获取和切换对话应用
- 优化对话应用切换后自动刷新会话列表功能
- 知识库管理页面新增下拉选择器，支持切换不同知识库
- API 层支持 app_id 参数传递，实现多应用会话隔离

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

app/components/dify-dataset-manager/layout.tsx

@@ -1,10 +1,12 @@
-import { Button, Tooltip } from 'antd';
+import { Button, Tooltip, Select, Spin } from 'antd';
 import {
     FileTextOutlined,
     SearchOutlined,
     SettingOutlined,
     ArrowLeftOutlined,
     DatabaseOutlined,
+    AppstoreOutlined,
+    SwapOutlined,
 } from '@ant-design/icons';
 import type { DatasetLayoutProps, MenuTab, MenuItem } from '~/types/dify-dataset-manager/layout';
 
@@ -19,28 +21,63 @@ export default function DatasetLayout({
     showBackButton = false,
     onBack,
     children,
+    availableDatasets = [],
+    loadingAvailableDatasets = false,
+    onDatasetChange,
 }: DatasetLayoutProps) {
     const menuItems: MenuItem[] = [
         { key: 'documents', icon: <FileTextOutlined />, label: '文档' },
         { key: 'retrieve', icon: <SearchOutlined />, label: '召回测试' },
+        { key: 'area-config', icon: <AppstoreOutlined />, label: '配置管理' },
         { key: 'settings', icon: <SettingOutlined />, label: '设置' },
     ];
 
+    // 是否显示知识库选择器（有多个知识库时显示）
+    const showDatasetSelector = availableDatasets.length > 1;
+
     return (
         <div className="dataset-layout">
             {/* 左侧侧边栏 */}
             <aside className="dataset-sidebar">
-                {/* 知识库信息 */}
+                {/* 知识库信息 / 选择器 */}
                 <div className="sidebar-header">
                     <div className="dataset-icon">
                         <DatabaseOutlined />
                     </div>
-                    <div className="dataset-info">
-                        <Tooltip title={dataset?.name} placement="right">
-                            <h2 className="dataset-name">{dataset?.name || '知识库'}</h2>
-                        </Tooltip>
-                        <span className="dataset-type">本地文档</span>
-                    </div>
+                    {showDatasetSelector ? (
+                        /* 多个知识库时显示下拉选择器 */
+                        <div className="dataset-selector">
+                            <Select
+                                value={dataset?.id}
+                                onChange={onDatasetChange}
+                                loading={loadingAvailableDatasets}
+                                className="dataset-select"
+                                placeholder="选择知识库"
+                                suffixIcon={<SwapOutlined />}
+                                popupMatchSelectWidth={false}
+                                dropdownStyle={{ minWidth: 200 }}
+                            >
+                                {availableDatasets.map(ds => (
+                                    <Select.Option key={ds.dataset_id} value={ds.dataset_id}>
+                                        <div className="dataset-option">
+                                            <span className="dataset-option-name">{ds.dataset_name}</span>
+                                            {ds.is_default && <span className="dataset-option-tag">默认</span>}
+                                            {ds.is_public && <span className="dataset-option-tag public">公共</span>}
+                                        </div>
+                                    </Select.Option>
+                                ))}
+                            </Select>
+                            <span className="dataset-type">本地文档</span>
+                        </div>
+                    ) : (
+                        /* 单个或无知识库时显示名称 */
+                        <div className="dataset-info">
+                            <Tooltip title={dataset?.name} placement="right">
+                                <h2 className="dataset-name">{dataset?.name || '知识库'}</h2>
+                            </Tooltip>
+                            <span className="dataset-type">本地文档</span>
+                        </div>
+                    )}
                 </div>
 
                 {/* 统计信息 */}