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

uv.lock

@@ -1,6 +1,11 @@
 version = 1
 revision = 3
 requires-python = ">=3.11"
+resolution-markers = [
+    "python_full_version >= '3.13'",
+    "python_full_version == '3.12.*'",
+    "python_full_version < '3.12'",
+]
 
 [[package]]
 name = "certifi"
@@ -460,7 +465,7 @@ requires-dist = [
     { name = "opencv-python" },
     { name = "questionary" },
     { name = "rich" },
-    { name = "scikit-learn" },
+    { name = "scikit-learn", specifier = ">=1.3.0" },
     { name = "uniface" },
 ]