Upgrade YOLO Models to v11 with User-Selectable Sizes

[rahulharpal1603]

Description

Update from YOLOv8n to YOLOv11 for improved performance and accuracy. Add a user preference system for model size selection (nano, small(default), medium).

Tasks

• Export YOLOv11 models (nano, small, medium) in ONNX format for object and face detection
• Create user_preferences property in the metadata table of the SQLite database
• Refactor YOLOv8.py to handle multiple model sizes
• Add API endpoint GET/PUT /user-preferences for model selection
• Update UI with model selection in onboarding and settings

Expected Outcome

Users can choose between different YOLO model sizes based on their hardware capabilities and performance needs.