feat: add SettingsScreen for configuration

lib/settings_screen.dart

@@ -0,0 +1,179 @@
+import 'package:flutter/material.dart';
+import 'package:traccar_client/bridge/location_bridge.dart';
+import 'package:traccar_client/preferences.dart';
+
+class SettingsScreen extends StatefulWidget {
+  const SettingsScreen({super.key});
+
+  @override
+  State<SettingsScreen> createState() => _SettingsScreenState();
+}
+
+class _SettingsScreenState extends State<SettingsScreen> {
+  late TextEditingController _serverUrlController;
+  late TextEditingController _deviceIdController;
+  late TextEditingController _passwordController;
+  late int _accuracy;
+  late int _distanceFilter;
+  late int _interval;
+  late int _heartbeat;
+  late bool _offlineBuffer;
+  late bool _stopDetection;
+
+  @override
+  void initState() {
+    super.initState();
+    _serverUrlController = TextEditingController(text: Preferences.serverUrl);
+    _deviceIdController = TextEditingController(text: Preferences.deviceId);
+    _passwordController = TextEditingController(text: Preferences.password);
+    _accuracy = Preferences.accuracy;
+    _distanceFilter = Preferences.distanceFilter;
+    _interval = Preferences.interval;
+    _heartbeat = Preferences.heartbeat;
+    _offlineBuffer = Preferences.offlineBuffer;
+    _stopDetection = Preferences.stopDetection;
+  }
+
+  @override
+  void dispose() {
+    _serverUrlController.dispose();
+    _deviceIdController.dispose();
+    _passwordController.dispose();
+    super.dispose();
+  }
+
+  Future<void> _saveSettings() async {
+    await Preferences.setServerUrl(_serverUrlController.text);
+    await Preferences.setDeviceId(_deviceIdController.text);
+    await Preferences.setPassword(_passwordController.text);
+    await Preferences.setAccuracy(_accuracy);
+    await Preferences.setDistanceFilter(_distanceFilter);
+    await Preferences.setInterval(_interval);
+    await Preferences.setHeartbeat(_heartbeat);
+    await Preferences.setOfflineBuffer(_offlineBuffer);
+    await Preferences.setStopDetection(_stopDetection);
+
+    await LocationBridge.updateConfig({
+      'serverUrl': _serverUrlController.text,
+      'deviceId': _deviceIdController.text,
+      'password': _passwordController.text,
+      'accuracy': _accuracy,
+      'distanceFilter': _distanceFilter,
+      'interval': _interval,
+      'heartbeat': _heartbeat,
+      'offlineBuffer': _offlineBuffer,
+      'stopDetection': _stopDetection,
+    });
+
+    if (mounted) {
+      ScaffoldMessenger.of(context).showSnackBar(
+        const SnackBar(content: Text('Settings saved')),
+      );
+    }
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: AppBar(
+        title: const Text('Settings'),
+      ),
+      body: ListView(
+        padding: const EdgeInsets.all(16),
+        children: [
+          _buildSectionHeader('Server'),
+          _buildTextField('Server URL', _serverUrlController),
+          _buildTextField('Device ID', _deviceIdController),
+          _buildTextField('Password', _passwordController, obscure: true),
+          const SizedBox(height: 16),
+          _buildSectionHeader('Location'),
+          _buildAccuracyDropdown(),
+          _buildNumberField('Distance Filter (m)', _distanceFilter, 0, 1000),
+          _buildNumberField('Update Interval (s)', _interval, 30, 3600),
+          _buildNumberField('Heartbeat (s)', _heartbeat, 60, 3600),
+          const SizedBox(height: 16),
+          _buildSectionHeader('Advanced'),
+          SwitchListTile(
+            title: const Text('Offline Buffering'),
+            subtitle: const Text('Queue locations when offline'),
+            value: _offlineBuffer,
+            onChanged: (v) => setState(() => _offlineBuffer = v),
+          ),
+          SwitchListTile(
+            title: const Text('Stop Detection'),
+            subtitle: const Text('Auto-stop when stationary'),
+            value: _stopDetection,
+            onChanged: (v) => setState(() => _stopDetection = v),
+          ),
+          const SizedBox(height: 24),
+          ElevatedButton(
+            onPressed: _saveSettings,
+            child: const Text('Save Settings'),
+          ),
+        ],
+      ),
+    );
+  }
+
+  Widget _buildSectionHeader(String title) {
+    return Padding(
+      padding: const EdgeInsets.only(top: 16, bottom: 8),
+      child: Text(
+        title,
+        style: Theme.of(context).textTheme.titleMedium?.copyWith(
+              fontWeight: FontWeight.bold,
+            ),
+      ),
+    );
+  }
+
+  Widget _buildTextField(String label, TextEditingController controller,
+      {bool obscure = false}) {
+    return TextField(
+      controller: controller,
+      decoration: InputDecoration(labelText: label),
+      obscureText: obscure,
+    );
+  }
+
+  Widget _buildAccuracyDropdown() {
+    return DropdownButtonFormField<int>(
+      value: _accuracy,
+      decoration: const InputDecoration(labelText: 'Accuracy'),
+      items: const [
+        DropdownMenuItem(value: 0, child: Text('High')),
+        DropdownMenuItem(value: 1, child: Text('High Accuracy')),
+        DropdownMenuItem(value: 2, child: Text('Balanced')),
+        DropdownMenuItem(value: 3, child: Text('Low')),
+      ],
+      onChanged: (v) => setState(() => _accuracy = v!),
+    );
+  }
+
+  Widget _buildNumberField(String label, int value, int min, int max) {
+    return TextFormField(
+      initialValue: value.toString(),
+      decoration: InputDecoration(labelText: label),
+      keyboardType: TextInputType.number,
+      validator: (v) {
+        final parsed = int.tryParse(v ?? '');
+        if (parsed == null || parsed < min || parsed > max) {
+          return 'Must be between $min and $max';
+        }
+        return null;
+      },
+      onSaved: (v) {
+        final parsed = int.tryParse(v ?? '');
+        if (parsed != null) {
+          if (label.contains('Distance')) {
+            _distanceFilter = parsed;
+          } else if (label.contains('Interval')) {
+            _interval = parsed;
+          } else if (label.contains('Heartbeat')) {
+            _heartbeat = parsed;
+          }
+        }
+      },
+    );
+  }
+}