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/INST-机构管理端/00-模块当前状态与开发指南.md

@@ -437,3 +437,6 @@ export const calculateAvailableQuota = async (tenantId: string) => {
 
 **🚀 敬请期待！**
 
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docs/03-业务模块/INST-机构管理端/README.md

@@ -310,3 +310,6 @@ https://platform.example.com/t/pharma-abc/login
 
 *最后更新：2026-01-11*
 
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