feat(ai): Day 7 — 会话持久化 Entity + Service

- 新增 3 个 SeaORM Entity: ai_chat_session / ai_chat_message / ai_tool_call_log
- ChatSessionService: create / list / get / close / rename
- ChatMessageService: save_message / list_messages / save_tool_call_log
- 参数封装为 SaveMessageParams / SaveToolCallLogParams 避免 clippy too_many_arguments
- AiState 注册 chat_session + chat_message 服务
- erp-server main.rs 初始化注入

crates/erp-ai/src/service/chat_session.rs

@@ -0,0 +1,101 @@
+use sea_orm::{
+    ActiveModelTrait, ColumnTrait, DatabaseConnection, EntityTrait, QueryFilter, QueryOrder, Set,
+};
+use uuid::Uuid;
+
+use crate::entity::ai_chat_session;
+
+pub struct ChatSessionService {
+    db: DatabaseConnection,
+}
+
+impl ChatSessionService {
+    pub fn new(db: DatabaseConnection) -> Self {
+        Self { db }
+    }
+
+    pub async fn create(
+        &self,
+        tenant_id: Uuid,
+        user_id: Uuid,
+        patient_id: Option<Uuid>,
+        title: Option<String>,
+    ) -> Result<ai_chat_session::Model, sea_orm::DbErr> {
+        let id = Uuid::now_v7();
+        let now = chrono::Utc::now();
+        let model = ai_chat_session::ActiveModel {
+            id: Set(id),
+            tenant_id: Set(tenant_id),
+            user_id: Set(user_id),
+            patient_id: Set(patient_id),
+            title: Set(title),
+            status: Set("active".to_string()),
+            metadata: Set(None),
+            created_at: Set(now),
+            updated_at: Set(now),
+            created_by: Set(Some(user_id)),
+            updated_by: Set(Some(user_id)),
+            deleted_at: Set(None),
+            version_lock: Set(1),
+        };
+        let result = model.insert(&self.db).await?;
+        Ok(result)
+    }
+
+    pub async fn list(
+        &self,
+        tenant_id: Uuid,
+        user_id: Uuid,
+    ) -> Result<Vec<ai_chat_session::Model>, sea_orm::DbErr> {
+        ai_chat_session::Entity::find()
+            .filter(ai_chat_session::Column::TenantId.eq(tenant_id))
+            .filter(ai_chat_session::Column::UserId.eq(user_id))
+            .filter(ai_chat_session::Column::DeletedAt.is_null())
+            .filter(ai_chat_session::Column::Status.ne("closed"))
+            .order_by_desc(ai_chat_session::Column::UpdatedAt)
+            .all(&self.db)
+            .await
+    }
+
+    pub async fn get(
+        &self,
+        tenant_id: Uuid,
+        session_id: Uuid,
+    ) -> Result<Option<ai_chat_session::Model>, sea_orm::DbErr> {
+        ai_chat_session::Entity::find()
+            .filter(ai_chat_session::Column::TenantId.eq(tenant_id))
+            .filter(ai_chat_session::Column::Id.eq(session_id))
+            .filter(ai_chat_session::Column::DeletedAt.is_null())
+            .one(&self.db)
+            .await
+    }
+
+    pub async fn close(&self, tenant_id: Uuid, session_id: Uuid) -> Result<bool, sea_orm::DbErr> {
+        let session = self.get(tenant_id, session_id).await?;
+        let Some(session) = session else {
+            return Ok(false);
+        };
+        let mut active: ai_chat_session::ActiveModel = session.into();
+        active.status = Set("closed".to_string());
+        active.updated_at = Set(chrono::Utc::now());
+        active.update(&self.db).await?;
+        Ok(true)
+    }
+
+    pub async fn rename(
+        &self,
+        tenant_id: Uuid,
+        session_id: Uuid,
+        new_title: String,
+    ) -> Result<bool, sea_orm::DbErr> {
+        let session = self.get(tenant_id, session_id).await?;
+        let Some(session) = session else {
+            return Ok(false);
+        };
+        let mut active: ai_chat_session::ActiveModel = session.into();
+        active.title = Set(Some(new_title));
+        active.updated_at = Set(chrono::Utc::now());
+        active.update(&self.db).await?;
+        Ok(true)
+    }
+}