Merge multiple QR code documentation files into a single comprehensive guide
that accurately reflects the current implementation. The consolidated guide:
- Combines information from qr-code-implementation-guide.mdc,
qr-code-handling-rule.mdc, and camera-implementation.md
- Clarifies the relationship between ContactQRScanView and ContactQRScanShowView
- Streamlines build configuration documentation
- Adds detailed sections on error handling, security, and best practices
- Improves organization and readability of implementation details
- Removes redundant information while preserving critical details
This change improves documentation maintainability and provides a single
source of truth for QR code implementation details.
