fix(pkb): fix create KB and upload issues - remove simulated upload, fix department mapping, add upload modal

Fixed issues:
- Remove simulateUpload function from DashboardPage Step 3
- Map department to description field when creating KB
- Add upload modal in WorkspacePage knowledge assets tab
- Fix DocumentUpload import path (../../stores to ../stores)

Known issue: Dify API validation error during document upload (file uploaded but DB record failed, needs investigation)

Testing: KB creation works, upload dialog opens correctly

docs/03-业务模块/DC-数据清洗整理/04-开发计划/工具C_缺失值处理功能_更新说明.md

@@ -191,6 +191,9 @@ method: 'mean' | 'median' | 'mode' | 'constant' | 'ffill' | 'bfill'
 
 
 
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