[LOW] Mobile BiometricContext exists but biometric auth not implemented

[kilodesodiq-arch]

Engineering Gap

app/mobile/src/contexts/BiometricContext.tsx is imported in App.tsx and wraps the app, but no biometric authentication flow is implemented. expo-local-authentication is in dependencies but not used in authentication workflows.

Codebase Evidence

• app/mobile/App.tsx line 14: BiometricProvider wraps app
• app/mobile/package.json: expo-local-authentication: ^55.0.9 installed
• app/mobile/src/contexts/BiometricContext.tsx: Context defined but may be stub

Risk Profile

Security feature present but unused. Missed opportunity for app-level security.

Remediation Strategy

Implement biometric lock on app open: require fingerprint/face before accessing sensitive screens. Add fallback PIN. Make optional via settings.

Success Conditions

• Biometric auth on app open
• Fallback PIN
• Settings toggle

Change Surface

Files: BiometricContext.tsx, App.tsx, SettingsScreen.tsx

Security Review

Adds app-level security. Biometric data stays on-device.

Completion Checklist

• Implementation completed
• Peer reviewed
• Tests passing
• Ready for merge