feat(mobile): Biometric Hardware-Secured Farmer Authentication in Mobile App

[hrshjswniii]

📌 Overview

This PR implements [feature] : Biometric Hardware-Secured Farmer Authentication in Mobile App bringing hardware-backed biometric unlock (TouchID / FaceID / Fingerprint) to the Expo mobile app, allowing smallholder farmers logging harvests in remote fields to authenticate sessions securely and quickly without typing passwords on field screens.

Key Changes Introduced:

1. Mobile Biometric Authentication Service:
   • Created [mobile/src/services/biometricAuthService.ts] wrapping expo-local-authentication and expo-secure-store for hardware capability checking, biometric prompt invocation, and secure key storage.
2. Profile Settings UI Integration:
   • Updated [mobile/app/(tabs)/profile.tsx] with an interactive Biometric Lock (फ़िंगरप्रिंट अनलॉक) toggle switch requiring biometric verification prior to enabling/disabling lock preferences.
3. Automated Verification Script:
   • Updated [mobile/verify-mobile-i18n.js] verifying biometric hardware check functions and profile screen integration (100% verification pass).

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🛠️ Type of Change

• ⛓️ Smart Contract (Solidity changes, Gas optimization)
• 💻 Frontend (UI/UX, React components, Tailwind)
• 📱 Mobile / Security (Expo React Native, Biometrics, Secure Store)
• 📄 Documentation (README, Roadmap updates)
• 🧪 Testing (Mobile verification script)

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🔗 Related Issue

Closes #1308

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🧪 Testing & Verification

• Smart Contracts: npx hardhat test passed? (N/A)
• Mobile: node verify-mobile-i18n.js passed? (Yes) — 100% parity & biometric hardware checks passing.
• Integration: Verified hardware biometric prompt invocation & toggle state persistence? (Yes).

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✅ PR Checklist

• My code follows the project's style guidelines.
• I have commented my code, particularly in complex areas (e.g., hardware biometric sensor checks & fallback passcodes).
• I have updated the documentation accordingly.
• My changes generate no new warnings.

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💬 Additional Notes

• Created [mobile/src/services/biometricAuthService.ts]
• Updated [mobile/app/(tabs)/profile.tsx]
• Updated [mobile/verify-mobile-i18n.js]

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