fix(practice): 修复结束会话接口 DetachedInstanceError

- 将 ORM 对象转换为 PracticeSessionResponse 后再返回
- 添加 COZE_WORKSPACE_ID 配置到 .env.ex

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/app/api/v1/practice.py

@@ -734,14 +734,27 @@ async def end_practice_session(
             except Exception:
                 pass
         
+        # 将 ORM 对象转换为响应格式，避免 DetachedInstanceError
+        session_data = PracticeSessionResponse(
+            id=session.id,
+            session_id=session.session_id,
+            user_id=session.user_id,
+            scene_id=session.scene_id,
+            scene_name=session.scene_name or "",
+            scene_type=session.scene_type,
+            conversation_id=session.conversation_id,
+            start_time=session.start_time,
+            end_time=session.end_time,
+            duration_seconds=session.duration_seconds or 0,
+            turns=session.turns or 0,
+            status=session.status,
+            created_at=session.created_at
+        )
+        
         return ResponseModel(
             code=200,
             message="会话已结束",
-            data={
-                "session": session,
-                "exp_result": exp_result,
-                "new_badges": new_badges
-            }
+            data=session_data
         )
     
     except HTTPException: