fix: 修复全量ruff/black/isort代码质量问题 (50个错误)

apps/worker/video_processing/pip_engine.py

@@ -20,20 +20,10 @@ from pathlib import Path
 from packages.domain.pip_config import POSITION_BOTTOM_CENTER  # noqa: E402, F401
 from packages.domain.pip_config import (
     ANIMATION_FADE,
-    ANIMATION_SCALE,
     ANIMATION_SLIDE_BOTTOM,
     ANIMATION_SLIDE_LEFT,
     ANIMATION_SLIDE_RIGHT,
     ANIMATION_SLIDE_TOP,
-    POSITION_BOTTOM_LEFT,
-    POSITION_BOTTOM_RIGHT,
-    POSITION_CENTER,
-    POSITION_CENTER_LEFT,
-    POSITION_CENTER_RIGHT,
-    POSITION_TOP_CENTER,
-    POSITION_TOP_LEFT,
-    POSITION_TOP_RIGHT,
-    PiPConfig,
     PiPLayerConfig,
 )
 from packages.domain.pip_config import (  # noqa: F401 — 向后兼容：保留模块级导出