fix(test): 修复MagicMock枚举导致的3个单元测试失败

根因：测试mock SessionLocal时未区分新/旧模板系统的model查询，
SQLAlchemyEditTemplateRepository.get()也会走到mock session并返回MagicMock，
导致_model_to_entity中EditTemplateStatus(model.status)枚举转换失败。

修复：mock session.query()增加side_effect，根据model类型返回不同结果：
- EditTemplateModel查询返回None（强制走旧模板系统fallback）
- TemplateModel查询返回mock template（测试目标路径）

影响测试：
- TestP1Validations.test_validate_template_exists_success
- TestTemplatePlanConfigLoading.test_load_template_config_assembles_three_fields
- TestTemplatePlanConfigLoading.test_load_template_config_only_bgm

tests/unit/test_oneclick_gen_p0_fixes.py

@@ -241,11 +241,27 @@ class TestP1Validations:
         mock_template.is_active = True
 
         session = MagicMock()
-        mock_session = MagicMock()
-        session.query.return_value = mock_session
-        filter_result = MagicMock()
-        mock_session.filter.return_value = filter_result
-        filter_result.first.return_value = mock_template
+
+        # EditTemplateModel 查询返回 None（走旧模板系统 fallback）
+        edit_query = MagicMock()
+        edit_filter = MagicMock()
+        edit_query.filter.return_value = edit_filter
+        edit_filter.first.return_value = None
+
+        # TemplateModel 查询返回 mock_template
+        old_query = MagicMock()
+        old_filter = MagicMock()
+        old_query.filter.return_value = old_filter
+        old_filter.first.return_value = mock_template
+
+        def _query_side_effect(model):
+            # 根据 model 类型返回不同的 query mock
+            name = getattr(model, "__name__", "")
+            if "EditTemplate" in name:
+                return edit_query
+            return old_query
+
+        session.query.side_effect = _query_side_effect
 
         with patch("worker_app.tasks.generation.SessionLocal", return_value=session):
             _validate_template_exists("tmpl_001")  # 不抛异常
@@ -255,11 +271,16 @@ class TestP1Validations:
         from worker_app.tasks.generation import _validate_template_exists
 
         session = MagicMock()
-        mock_session = MagicMock()
-        session.query.return_value = mock_session
-        filter_result = MagicMock()
-        mock_session.filter.return_value = filter_result
-        filter_result.first.return_value = None
+
+        # 两个系统查询都返回 None
+        def _query_side_effect(model):
+            q = MagicMock()
+            f = MagicMock()
+            q.filter.return_value = f
+            f.first.return_value = None
+            return q
+
+        session.query.side_effect = _query_side_effect
 
         with patch("worker_app.tasks.generation.SessionLocal", return_value=session):
             with pytest.raises(ValueError, match="模板不存在"):
@@ -431,11 +452,26 @@ class TestTemplatePlanConfigLoading:
 
     def _mock_session(self, template):
         session = MagicMock()
-        mock_query = MagicMock()
-        session.query.return_value = mock_query
-        filter_result = MagicMock()
-        mock_query.filter.return_value = filter_result
-        filter_result.first.return_value = template
+
+        # EditTemplateModel 查询返回 None（走旧模板系统 fallback）
+        edit_query = MagicMock()
+        edit_filter = MagicMock()
+        edit_query.filter.return_value = edit_filter
+        edit_filter.first.return_value = None
+
+        # TemplateModel 查询返回 template（旧模板系统）
+        old_query = MagicMock()
+        old_filter = MagicMock()
+        old_query.filter.return_value = old_filter
+        old_filter.first.return_value = template
+
+        def _query_side_effect(model):
+            name = getattr(model, "__name__", "")
+            if "EditTemplate" in name:
+                return edit_query
+            return old_query
+
+        session.query.side_effect = _query_side_effect
         return session
 
     def test_load_template_config_assembles_three_fields(self):
@@ -503,11 +539,15 @@ class TestTemplatePlanConfigLoading:
         from worker_app.tasks.generation import _load_template_plan_config
 
         session = MagicMock()
-        mock_query = MagicMock()
-        session.query.return_value = mock_query
-        filter_result = MagicMock()
-        mock_query.filter.return_value = filter_result
-        filter_result.first.return_value = None
+
+        def _query_side_effect(model):
+            q = MagicMock()
+            f = MagicMock()
+            q.filter.return_value = f
+            f.first.return_value = None
+            return q
+
+        session.query.side_effect = _query_side_effect
 
         with patch("worker_app.tasks.generation.SessionLocal", return_value=session):
             result = _load_template_plan_config("tmpl_nonexist")