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-server/migration/src/lib.rs

@@ -155,6 +155,7 @@ mod m20260518_000150_seed_ai_config_permission;
 mod m20260518_000151_fix_ai_config_menu_parent;
 mod m20260518_000152_seed_ai_provider_permission;
 mod m20260518_000153_ai_health_butler_v2;
+mod m20260519_000154_seed_ai_knowledge_permissions;
 
 pub struct Migrator;
 
@@ -317,6 +318,7 @@ impl MigratorTrait for Migrator {
             Box::new(m20260518_000151_fix_ai_config_menu_parent::Migration),
             Box::new(m20260518_000152_seed_ai_provider_permission::Migration),
             Box::new(m20260518_000153_ai_health_butler_v2::Migration),
+            Box::new(m20260519_000154_seed_ai_knowledge_permissions::Migration),
         ]
     }
 }