fix(test): 修复test_dedup_pure收集阶段db连接副作用

根因：video_processing/dedup.py 顶层import worker_app.db，
而 db.py 模块加载时就执行 ensure_database_exists() 触发数据库连接。
纯函数测试不需要任何db/celery/cv2依赖。

修复：在测试模块顶部预先mock掉所有有副作用的模块
（cv2/celery/sqlalchemy/worker_app/packages.adapters/packages.shared），
确保 import dedup 时不会触发真实的数据库连接。

20 passed ✅

tests/unit/test_dedup_pure.py

@@ -8,9 +8,65 @@ from unittest.mock import MagicMock
 import numpy as np
 import pytest
 
-# 模块级mock cv2（dedup模块import时需要）
+# 模块级mock有副作用的依赖（纯算法测试不需要db/celery/cv2）
+# 注意：必须在 import dedup 前全部 mock 完，避免链式导入触发db连接
+
+# cv2（视频处理依赖，纯算法测试不需要）
 sys.modules["cv2"] = MagicMock()
 
+# celery 及其子模块
+_mock_celery = MagicMock()
+_mock_celery.Task = MagicMock
+_mock_celery.Celery = MagicMock
+sys.modules["celery"] = _mock_celery
+
+# sqlalchemy 作为包结构 mock
+_mock_sqla = MagicMock()
+_mock_sqla.__path__ = []
+_mock_sqla.__package__ = "sqlalchemy"
+_mock_sqla_orm = MagicMock()
+_mock_sqla_orm.__path__ = []
+_mock_sqla_orm.Session = MagicMock
+_mock_sqla_engine = MagicMock()
+sys.modules["sqlalchemy"] = _mock_sqla
+sys.modules["sqlalchemy.orm"] = _mock_sqla_orm
+sys.modules["sqlalchemy.engine"] = _mock_sqla_engine
+sys.modules["sqlalchemy.ext"] = MagicMock()
+sys.modules["sqlalchemy.ext.declarative"] = MagicMock()
+
+# worker_app 及其子模块（避免导入时触发数据库连接）
+_mock_worker_app = MagicMock()
+_mock_worker_app.__path__ = []
+_mock_worker_db = MagicMock()
+_mock_worker_db.SessionLocal = MagicMock()
+_mock_worker_celery = MagicMock()
+_mock_worker_celery.celery_app = MagicMock()
+_mock_worker_core = MagicMock()
+_mock_worker_core.__path__ = []
+_mock_worker_config = MagicMock()
+_mock_worker_config.get_settings = MagicMock(return_value=MagicMock())
+sys.modules["worker_app"] = _mock_worker_app
+sys.modules["worker_app.db"] = _mock_worker_db
+sys.modules["worker_app.celery_app"] = _mock_worker_celery
+sys.modules["worker_app.core"] = _mock_worker_core
+sys.modules["worker_app.core.config"] = _mock_worker_config
+
+# packages.adapters.sqlalchemy_impl（整个包mock掉）
+_mock_sqla_impl = MagicMock()
+_mock_sqla_impl.__path__ = []
+sys.modules["packages.adapters.sqlalchemy_impl"] = _mock_sqla_impl
+sys.modules["packages.adapters.sqlalchemy_impl.generated_video_repository"] = MagicMock()
+sys.modules["packages.adapters.sqlalchemy_impl.schema_guard"] = MagicMock()
+
+# packages.shared
+_mock_packages_shared = MagicMock()
+_mock_packages_shared.__path__ = []
+_mock_shared_config = MagicMock()
+_mock_shared_config.get_shared_settings = MagicMock(return_value=MagicMock())
+sys.modules["packages.shared"] = _mock_packages_shared
+sys.modules["packages.shared.config"] = _mock_shared_config
+sys.modules["packages.shared.storage"] = MagicMock()
+
 from video_processing.dedup import (  # noqa: E402
     VideoDeduplicator,
     VideoFingerprint,