feat(kiosk): numeric keypad for PIN entry

Kiosk/lib/screens/main_screen.dart

@@ -9,6 +9,7 @@ import 'package:kiosk/models/product.dart';
 import 'package:kiosk/models/order.dart' as model; // Alias to avoid conflict if needed
 import 'package:kiosk/screens/payment_screen.dart';
 import 'package:kiosk/screens/manual_barcode_dialog.dart';
+import 'package:kiosk/screens/pin_input_dialog.dart';
 import 'package:kiosk/screens/no_barcode_products_dialog.dart';
 import 'package:kiosk/screens/settings_screen.dart';
 import 'package:mobile_scanner/mobile_scanner.dart';
@@ -182,42 +183,12 @@ class _MainScreenState extends State<MainScreen> {
     final expected = _settingsService.getPin();
     if (expected == null || expected.isEmpty) return true;
 
-    final l10n = AppLocalizations.of(context)!;
-    final controller = TextEditingController();
-    final ok = await showDialog<bool>(
+    final result = await showDialog<bool>(
       context: context,
       barrierDismissible: false,
-      builder: (dialogContext) {
-        return AlertDialog(
-          title: Text(l10n.adminConfirm),
-          content: TextField(
-            controller: controller,
-            obscureText: true,
-            keyboardType: TextInputType.number,
-            decoration: InputDecoration(labelText: l10n.enterPin),
-          ),
-          actions: [
-            TextButton(
-              onPressed: () => Navigator.pop(dialogContext, false),
-              child: Text(l10n.cancel),
-            ),
-            TextButton(
-              onPressed: () {
-                if (controller.text.trim() == expected) {
-                  Navigator.pop(dialogContext, true);
-                } else {
-                  ScaffoldMessenger.of(context).showSnackBar(
-                    SnackBar(content: Text(l10n.invalidPin)),
-                  );
-                }
-              },
-              child: Text(l10n.confirm),
-            ),
-          ],
-        );
-      },
+      builder: (dialogContext) => PinInputDialog(expectedPin: expected),
     );
-    return ok ?? false;
+    return result ?? false;
   }
 
   Future<void> _resumePendingPaymentIfAny() async {

Kiosk/lib/screens/pin_input_dialog.dart

@@ -0,0 +1,192 @@
+import 'package:flutter/material.dart';
+import 'package:kiosk/l10n/app_localizations.dart';
+
+class PinInputDialog extends StatefulWidget {
+  final String? expectedPin;
+
+  const PinInputDialog({
+    super.key,
+    this.expectedPin,
+  });
+
+  @override
+  State<PinInputDialog> createState() => _PinInputDialogState();
+}
+
+class _PinInputDialogState extends State<PinInputDialog> {
+  String _input = '';
+
+  void _onKeyTap(String key) {
+    if (_input.length >= 6) return;
+    setState(() {
+      _input += key;
+    });
+  }
+
+  void _onBackspace() {
+    if (_input.isNotEmpty) {
+      setState(() {
+        _input = _input.substring(0, _input.length - 1);
+      });
+    }
+  }
+
+  void _onClear() {
+    setState(() {
+      _input = '';
+    });
+  }
+
+  void _onConfirm() {
+    if (widget.expectedPin != null) {
+      if (_input == widget.expectedPin) {
+        Navigator.pop(context, true);
+      } else {
+        final l10n = AppLocalizations.of(context)!;
+        ScaffoldMessenger.of(context).showSnackBar(
+           SnackBar(content: Text(l10n.invalidPin)),
+        );
+        _onClear();
+      }
+    } else {
+      Navigator.pop(context, _input);
+    }
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final l10n = AppLocalizations.of(context)!;
+
+    return Dialog(
+      shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(16)),
+      child: ConstrainedBox(
+        constraints: BoxConstraints(
+          maxWidth: 420,
+        ),
+        child: Padding(
+          padding: const EdgeInsets.all(24),
+          child: Column(
+            mainAxisSize: MainAxisSize.min,
+            children: [
+              Text(
+                l10n.adminConfirm,
+                style: const TextStyle(fontSize: 24, fontWeight: FontWeight.bold),
+              ),
+              const SizedBox(height: 8),
+              Text(l10n.enterPin, style: const TextStyle(color: Colors.grey)),
+              const Divider(height: 20),
+              Container(
+                width: double.infinity,
+                padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 16),
+                decoration: BoxDecoration(
+                  border: Border.all(color: Colors.grey),
+                  borderRadius: BorderRadius.circular(8),
+                ),
+                child: Text(
+                  _input.isEmpty ? '----' : '*' * _input.length,
+                  style: TextStyle(
+                    fontSize: 32,
+                    color: _input.isEmpty ? Colors.grey : Colors.black,
+                    letterSpacing: 8,
+                  ),
+                  textAlign: TextAlign.center,
+                ),
+              ),
+              const SizedBox(height: 12),
+              SizedBox(
+                height: 240,
+                child: GridView.count(
+                  crossAxisCount: 3,
+                  childAspectRatio: 2.35,
+                  mainAxisSpacing: 10,
+                  crossAxisSpacing: 10,
+                  physics: const NeverScrollableScrollPhysics(),
+                  children: [
+                    for (var i = 1; i <= 9; i++) _buildKey(i.toString()),
+                    _buildBackspaceKey(),
+                    _buildKey('0'),
+                    _buildActionButton(l10n.clear, Colors.orange, _onClear),
+                  ],
+                ),
+              ),
+              const SizedBox(height: 12),
+              Row(
+                children: [
+                  Expanded(
+                    child: SizedBox(
+                      height: 56,
+                      child: _buildActionButton(
+                        l10n.cancel,
+                        Colors.grey,
+                        () => Navigator.pop(context, false),
+                      ),
+                    ),
+                  ),
+                  const SizedBox(width: 16),
+                  Expanded(
+                    child: SizedBox(
+                      height: 56,
+                      child: _buildActionButton(l10n.confirm, Colors.blue, _onConfirm),
+                    ),
+                  ),
+                ],
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+
+  Widget _buildBackspaceKey() {
+    return InkWell(
+      onTap: _onBackspace,
+      borderRadius: BorderRadius.circular(8),
+      child: Container(
+        decoration: BoxDecoration(
+          color: Colors.grey[300],
+          borderRadius: BorderRadius.circular(8),
+        ),
+        alignment: Alignment.center,
+        child: const Icon(Icons.backspace, size: 24),
+      ),
+    );
+  }
+
+  Widget _buildKey(String label, {VoidCallback? onTap}) {
+    return InkWell(
+      onTap: onTap ?? () => _onKeyTap(label),
+      borderRadius: BorderRadius.circular(8),
+      child: Container(
+        decoration: BoxDecoration(
+          color: Colors.grey[200],
+          borderRadius: BorderRadius.circular(8),
+          boxShadow: [
+            BoxShadow(
+              color: Colors.black.withValues(alpha: 0.1),
+              blurRadius: 2,
+              offset: const Offset(1, 1),
+            ),
+          ],
+        ),
+        alignment: Alignment.center,
+        child: Text(label, style: const TextStyle(fontSize: 28, fontWeight: FontWeight.bold)),
+      ),
+    );
+  }
+
+  Widget _buildActionButton(String label, Color color, VoidCallback onTap) {
+    return InkWell(
+      onTap: onTap,
+      borderRadius: BorderRadius.circular(8),
+      child: Container(
+        decoration: BoxDecoration(
+          color: color,
+          borderRadius: BorderRadius.circular(8),
+        ),
+        alignment: Alignment.center,
+        child: Text(label, style: const TextStyle(fontSize: 18, color: Colors.white, fontWeight: FontWeight.bold)),
+      ),
+    );
+  }
+}