feat(admin): Implement System Knowledge Base management module
Features:
- Backend: SystemKbService with full CRUD (knowledge bases + documents)
- Backend: 8 RESTful API endpoints (list/detail/create/update/delete/upload/download)
- Backend: OSS storage integration (system/knowledge-bases/{kbId}/{docId})
- Backend: RAG engine integration (document parsing, chunking, vectorization)
- Frontend: SystemKbListPage with card-based layout
- Frontend: SystemKbDetailPage with document management table
- Frontend: Master-Detail UX pattern for better user experience
- Document upload (single/batch), download (preserving original filename), delete
Technical:
- Database migration for system_knowledge_bases and system_kb_documents tables
- OSSAdapter.getSignedUrl with Content-Disposition for original filename
- Reuse RAG engine from common/rag for document processing
Tested: Local environment verified, all features working
HaHafeng
0d9e6b9922