Add 'Gunakan Sidik Jari' retry button on login (shown when biometric enabled+available). Loads biometric flags at init.

lib/auth_screen.dart

@@ -21,6 +21,8 @@ class _AuthScreenState extends State<AuthScreen> {
   bool _busy = false;
   String? _error;
   String? _bioMsg;
+  bool _biometricAvailable = false;
+  bool _biometricEnabled = false;
 
   @override
   void initState() {
@@ -32,10 +34,16 @@ class _AuthScreenState extends State<AuthScreen> {
   Future<void> _initMode() async {
     final registered = await widget.auth.isRegistered();
     if (!mounted) return;
-    setState(() => _isLogin = registered);
+    final avail = await widget.auth.canUseBiometrics();
+    final enabled = await widget.auth.isBiometricEnabled();
+    setState(() {
+      _isLogin = registered;
+      _biometricAvailable = avail;
+      _biometricEnabled = enabled;
+    });
     // If already registered and biometric is enabled, prompt fingerprint
     // automatically (unless a valid session already skips to dashboard).
-    if (registered && await widget.auth.isBiometricEnabled()) {
+    if (registered && enabled) {
       final timeout = await widget.auth.getTimeoutMinutes();
       final valid = await widget.auth.hasValidSession(timeout);
       if (!valid) {
@@ -154,10 +162,26 @@ class _AuthScreenState extends State<AuthScreen> {
             const SizedBox(height: 12),
             _busy
                 ? const CircularProgressIndicator()
-                : ElevatedButton(
+                : Column(
+                    children: [
+                      ElevatedButton(
                         onPressed: _submit,
                         child: Text(_isLogin ? 'Masuk' : 'Daftar'),
                       ),
+                      // Biometric retry button (only when enabled + registered)
+                      if (_isLogin &&
+                          _biometricAvailable &&
+                          _biometricEnabled)
+                        TextButton.icon(
+                          onPressed: () {
+                            setState(() => _bioMsg = null);
+                            _promptBiometricOnOpen();
+                          },
+                          icon: const Icon(Icons.fingerprint),
+                          label: const Text('Gunakan Sidik Jari'),
+                        ),
+                    ],
+                  ),
           ],
         ),
       ),