feat: add YuNet detector option, multi-scale detection, and streamlined CLI

- Add YuNet face detector as alternative option (built into OpenCV)
- Add multi-scale detection (1.0x + 1.5x) to catch faces at different distances
- Add NMS to remove duplicate detections from multi-scale
- Move frame interval and clustering settings to advanced options
- Increase default blur padding from 25% to 40%
- Change default frame interval from 30 to 15
- Change default confidence threshold from 0.7 to 0.8
- Add limitations section to README (extreme angles, small faces, motion blur)
- Require scikit-learn>=1.3.0 for HDBSCAN support

pyproject.toml

@@ -8,7 +8,7 @@ dependencies = [
     "uniface",
     "numpy",
     "opencv-python",
-    "scikit-learn",
+    "scikit-learn>=1.3.0",
     "rich",
     "questionary",
 ]