multiple updates

- colour theme implemented. ThemeService based global switching for future light detection triggers
- test flipflop service for various fun
- navigator widget class with state switching

pi/ui/lib/widgets/navigator_widget.dart

@@ -0,0 +1,59 @@
+import 'dart:io';
+import 'package:flutter/material.dart';
+import '../services/config_service.dart';
+
+/// Displays the navigator character with emotion support.
+///
+/// Use a GlobalKey to control emotions from parent:
+/// ```dart
+/// final _navigatorKey = GlobalKey<NavigatorWidgetState>();
+/// NavigatorWidget(key: _navigatorKey)
+/// // Later:
+/// _navigatorKey.currentState?.setEmotion('happy');
+/// ```
+class NavigatorWidget extends StatefulWidget {
+  const NavigatorWidget({super.key});
+
+  @override
+  State<NavigatorWidget> createState() => NavigatorWidgetState();
+}
+
+class NavigatorWidgetState extends State<NavigatorWidget> {
+  String _emotion = 'default';
+
+  /// Change the displayed emotion.
+  /// Image file must exist at: {assetsPath}/navigator/{navigator}/{emotion}.png
+  void setEmotion(String emotion) {
+    if (emotion != _emotion) {
+      setState(() => _emotion = emotion);
+    }
+  }
+
+  /// Reset to default emotion
+  void reset() => setEmotion('default');
+
+  /// Current emotion
+  String get emotion => _emotion;
+
+  @override
+  Widget build(BuildContext context) {
+    final config = ConfigService.instance;
+    final basePath = '${config.assetsPath}/navigator/${config.navigator}';
+
+    return Image.file(
+      File('$basePath/$_emotion.png'),
+      fit: BoxFit.contain,
+      errorBuilder: (context, error, stackTrace) {
+        // Fallback: try default.png if specific emotion missing
+        if (_emotion != 'default') {
+          return Image.file(
+            File('$basePath/default.png'),
+            fit: BoxFit.contain,
+            errorBuilder: (_, __, ___) => const SizedBox.shrink(),
+          );
+        }
+        return const SizedBox.shrink();
+      },
+    );
+  }
+}