feat(ai): Phase 3A RAG 知识库 — CRUD API + Agent Tool + 向量知识源 + 前端管理页

- 知识库 REST API: 10 个端点 (references/guides CRUD + re-embed)
- search_medical_knowledge Agent Tool: 语义检索参考资料和临床指南
- VectorKnowledgeSource: 实现 KnowledgeSource trait，自动降级
- 沙箱配置: Patient/MedicalStaff 允许使用知识库检索
- 前端 AiKnowledgePage: Tabs(参考资料/临床指南) + Table + Modal CRUD
- 权限码 seed 迁移: ai.knowledge.list + ai.knowledge.manage + 菜单

crates/erp-ai/src/state.rs

@@ -9,6 +9,7 @@ use crate::service::analysis::AnalysisService;
 use crate::service::cache::CacheService;
 use crate::service::feature_flag_service::FeatureFlagService;
 use crate::service::insight_service::InsightService;
+use crate::service::knowledge::KnowledgeService;
 use crate::service::prompt::PromptService;
 use crate::service::quota::QuotaService;
 use crate::service::risk_service::RiskService;
@@ -30,4 +31,5 @@ pub struct AiState {
     pub risk_service: Arc<RiskService>,
     pub insight_service: Arc<InsightService>,
     pub feature_flags: Arc<FeatureFlagService>,
+    pub knowledge: Arc<KnowledgeService>,
 }