Add full-featured example with person detection, AI prompts, and file upload

[tomershlasky]

Summary

• Adds a 4th example (examples/full-featured/) that combines all features from the existing 3 examples
• Person detection — auto-connects/disconnects using MediaPipe pose detection, saves credits when no one is in frame
• AI-enhanced prompts — GPT-4o-mini generates descriptive try-on prompts from garment image + camera frame
• File upload — users can upload their own garment images and get AI-generated prompts automatically
• Product catalog sidebar with editable prompt bar
• Updates root README to reference the new 4th example

Test plan

• next build compiles successfully
• Open http://localhost:3000, verify sidebar with upload button + product grid renders
• Step in front of camera, verify person detection triggers connection
• Click a product, verify AI prompt is generated and garment is applied
• Upload a custom garment image, verify it gets an AI-generated prompt
• Step away from camera, verify disconnection; step back, verify reconnect + last garment re-applied
• Edit prompt text and click Apply, verify garment updates