Fork facesaver -> anime-facesaver: real anime face detector instead of COCO 'person' proxy

Original saved any frame with a big COCO person box (heads, hands,
shoes). Switches to yolov8x6_animeface (HF: Fuyucchi), keeps the
scene-change gate, adds --gpu pinning via CUDA_VISIBLE_DEVICES before
torch init, --download-model, --preview-dir QC mode, optional edge
margin and min face-area fraction.

.gitignore

@@ -0,0 +1,8 @@
+.venv/
+__pycache__/
+*.pyc
+models/
+output/
+preview/
+*.pt
+*.part