feat: Add AI model files with Git LFS

Add 5 YOLO model files for video detection:
- fire_detection/best.pt (61MB) - YOLOv10 fire and smoke detection
- helmet_detection/yolov8n.pt (6.2MB) - YOLOv8 helmet detection
- crowd_detection/yolov8l.pt (84MB) - YOLOv8 crowd gathering detection
- smoking_detection/smoking_yolov8n.pt (5.9MB) - YOLOv8 smoking detection
- loitering_detection/yolov8n.pt (6.2MB) - YOLOv8 loitering detection

Configure Git LFS to track *.pt files
Update .gitignore to allow .pt files (now managed by LFS)

.gitattributes

@@ -0,0 +1 @@
+*.pt filter=lfs diff=lfs merge=lfs -text

.gitignore

@@ -46,8 +46,8 @@ coverage/
 # Turbo
 .turbo/
 
-# Model files (large files)
+# Model files (now managed by Git LFS)
-*.pt
+# *.pt files are tracked by Git LFS
 *.onnx
 *.pth
 *.weights