Added OS-level authentication with optional App PIN / Offline PIN fallback

src/screen/authorised/deviceAuth.ts

@@ -0,0 +1,40 @@
+import ReactNativeBiometrics from 'react-native-biometrics';
+
+const rnBiometrics = new ReactNativeBiometrics({
+    allowDeviceCredentials: true, // 👈 IMPORTANT (PIN / Pattern)
+});
+
+export const authenticateWithDeviceLock = async () => {
+    try {
+        const { available } = await rnBiometrics.isSensorAvailable();
+
+        if (!available) {
+            return {
+                success: false,
+                message: 'Device lock is not available',
+            };
+        }
+
+        const result = await rnBiometrics.simplePrompt({
+            promptMessage: 'Authenticate to continue',
+            cancelButtonText: 'Cancel',
+        });
+
+        if (result.success) {
+            return {
+                success: true,
+                message: 'Authentication successful',
+            };
+        } else {
+            return {
+                success: false,
+                message: 'Authentication cancelled',
+            };
+        }
+    } catch (error: any) {
+        return {
+            success: false,
+            message: error?.message || 'Authentication failed',
+        };
+    }
+};