fix: raise BLUR_THRESHOLD default from 100 to 120 to match Frigate's floor

Frigate classifies images with Laplacian variance < 120 as "very blurry"
and its own docs recommend avoiding blurry training data. Winnow was
accepting images in the 100-120 range that Frigate considers too blurry.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/test_config.py

@@ -19,7 +19,7 @@ def test_config_loads_defaults(monkeypatch):
     assert cfg.YEARS_FILTER == 10
     assert cfg.MIN_FACE_WIDTH == 90
     assert cfg.MIN_FACE_COUNT == 0
-    assert cfg.BLUR_THRESHOLD == 100.0
+    assert cfg.BLUR_THRESHOLD == 120.0
     assert cfg.MIN_CONFIDENCE == 0.7
     assert cfg.MAX_AUTO_IMAGES == 80
     assert cfg.QUALITY_REPLACEMENT is True