Change polling interval to retrieve BusiLight status (#3)

Implement a more agressive polling interval to retrieve BusiLight status.
From (in sec.):
```
- min: 0
- max: 60
- default: 5
- divisions: 12
```
to (in sec.):
```
- min: 0
- max: 2
- default: 1
- divisions: 4
```

Reviewed-on: #3

lib/providers/busylight_provider.dart

@@ -10,7 +10,7 @@ import '../services/busylight_service.dart';
 const _kHostKey        = 'busylight_host';
 const _kDefaultHost    = 'http://igox-busylight.local';
 const _kPollIntervalKey     = 'busylight_poll_interval';
-const _kDefaultPollInterval = 5; // seconds
+const _kDefaultPollInterval = 1.0; // seconds
 
 final sharedPreferencesProvider = FutureProvider<SharedPreferences>(
   (_) => SharedPreferences.getInstance(),
@@ -21,9 +21,9 @@ final deviceHostProvider = StateProvider<String>((ref) {
   return prefs?.getString(_kHostKey) ?? _kDefaultHost;
 });
 
-final pollIntervalProvider = StateProvider<int>((ref) {
+final pollIntervalProvider = StateProvider<double>((ref) {
   final prefs = ref.watch(sharedPreferencesProvider).valueOrNull;
-  return prefs?.getInt(_kPollIntervalKey) ?? _kDefaultPollInterval;
+  return prefs?.getDouble(_kPollIntervalKey) ?? _kDefaultPollInterval.toDouble();
 });
 
 // ── Service ──────────────────────────────────────────────────────────────────
@@ -161,10 +161,11 @@ class PollingNotifier extends StateNotifier<void> {
   Timer? _timer;
 
   void _start() {
-    final interval = _ref.read(pollIntervalProvider);
+    final intervalSeconds = _ref.read(pollIntervalProvider);
+    final intervalMillis = (intervalSeconds * 1000).toInt();
     _timer?.cancel();
-    if (interval <= 0) return;
-    _timer = Timer.periodic(Duration(seconds: interval), (_) => _poll());
+    if (intervalMillis <= 0) return;
+    _timer = Timer.periodic(Duration(milliseconds: intervalMillis), (_) => _poll());
   }
 
   void restart() => _start();

lib/screens/settings_screen.dart

@@ -14,7 +14,7 @@ class SettingsScreen extends ConsumerStatefulWidget {
 
 class _SettingsScreenState extends ConsumerState<SettingsScreen> {
   late TextEditingController _hostController;
-  late int _pollInterval;
+  late double _pollInterval;
   bool _startWithSession = false;
 
   @override
@@ -48,7 +48,7 @@ class _SettingsScreenState extends ConsumerState<SettingsScreen> {
 
     final prefs = await SharedPreferences.getInstance();
     await prefs.setString('busylight_host', host);
-    await prefs.setInt('busylight_poll_interval', _pollInterval);
+    await prefs.setDouble('busylight_poll_interval', _pollInterval);
 
     if (mounted) {
       ScaffoldMessenger.of(context).showSnackBar(
@@ -58,10 +58,10 @@ class _SettingsScreenState extends ConsumerState<SettingsScreen> {
     }
   }
 
-  String _intervalLabel(int seconds) {
-    if (seconds == 0) return 'Off';
-    if (seconds < 60) return '${seconds}s';
-    return '${seconds ~/ 60}m';
+  String _intervalLabel(double seconds) {
+    if (seconds == 0.0) return 'Off';
+    if (seconds < 2.0) return '${seconds}s';
+    return '${ (seconds)}s';
   }
 
   @override
@@ -124,21 +124,21 @@ class _SettingsScreenState extends ConsumerState<SettingsScreen> {
                 overlayColor: Colors.amber.withOpacity(0.2),
               ),
               child: Slider(
-                value: _pollInterval.toDouble(),
-                min: 0,
-                max: 60,
-                divisions: 12,
-                onChanged: (v) => setState(() => _pollInterval = v.round()),
+                value: _pollInterval,
+                min: 0.0,
+                max: 2.0,
+                divisions: 4,
+                onChanged: (v) => setState(() => _pollInterval = v),
               ),
             ),
             Row(
               mainAxisAlignment: MainAxisAlignment.spaceBetween,
               children: [
                 Text('Off', style: TextStyle(color: Colors.grey.shade600, fontSize: 11)),
-                Text('5s',  style: TextStyle(color: Colors.grey.shade600, fontSize: 11)),
-                Text('10s', style: TextStyle(color: Colors.grey.shade600, fontSize: 11)),
-                Text('30s', style: TextStyle(color: Colors.grey.shade600, fontSize: 11)),
-                Text('1m',  style: TextStyle(color: Colors.grey.shade600, fontSize: 11)),
+                Text('0.5s',  style: TextStyle(color: Colors.grey.shade600, fontSize: 11)),
+                Text('1s', style: TextStyle(color: Colors.grey.shade600, fontSize: 11)),
+                Text('1.5s', style: TextStyle(color: Colors.grey.shade600, fontSize: 11)),
+                Text('2s',  style: TextStyle(color: Colors.grey.shade600, fontSize: 11)),
               ],
             ),
             const SizedBox(height: 6),