feat(pkb): Complete PKB module frontend migration with V3 design

Summary:
- Implement PKB Dashboard and Workspace pages based on V3 prototype
- Add single-layer header with integrated Tab navigation
- Implement 3 work modes: Full Text, Deep Read, Batch Processing
- Integrate Ant Design X Chat component for AI conversations
- Create BatchModeComplete with template selection and document processing
- Add compact work mode selector with dropdown design

Backend:
- Migrate PKB controllers and services to /modules/pkb structure
- Register v2 API routes at /api/v2/pkb/knowledge
- Maintain dual API routes for backward compatibility

Technical details:
- Use Zustand for state management
- Handle SSE streaming responses for AI chat
- Support document selection for Deep Read mode
- Implement batch processing with progress tracking

Known issues:
- Batch processing API integration pending
- Knowledge assets page navigation needs optimization

Status: Frontend functional, pending refinement

frontend-v2/src/framework/modules/moduleRegistry.ts

@@ -42,9 +42,9 @@ export const MODULES: ModuleDefinition[] = [
     path: '/knowledge-base',
     icon: FolderOpenOutlined,
     component: lazy(() => import('@/modules/pkb')),
-    placeholder: true, // 后续重写
+    placeholder: false, // V5.0设计已完成实现 ✅
     requiredVersion: 'basic',
-    description: '个人知识库管理系统',
+    description: '个人知识库管理系统（支持全文阅读、逐篇精读、批处理）',
   },
   {
     id: 'data-cleaning',