chore: move model storage into project models/ directory

Models now live in <project>/models/ instead of ~/.8cut_models/ so
everything stays self-contained. Updated .gitignore to exclude
models/, .venv/, *.joblib, and *.pt.

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

core/audio_scan.py

@@ -9,7 +9,7 @@ from .paths import _log
 
 _SR = 16000           # lower sr = faster
 _WINDOW = 8.0         # seconds
-_MODEL_DIR = os.path.join(os.path.expanduser("~"), ".8cut_models")
+_MODEL_DIR = os.path.join(os.path.dirname(os.path.dirname(os.path.abspath(__file__))), "models")
 _W2V_CACHE_DIR = os.path.join(os.path.expanduser("~"), ".8cut_cache", "w2v")
 
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