Implements device authorization registration and verification:
- AES-256-GCM + PBKDF2 decryption of .xuqmlicense files
- Keychain storage for token and deviceId
- UIDevice.identifierForVendor for device ID
- 10-minute cache with offline fallback
- LicenseResult sealed type (success/error)
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>