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/theme/app_theme.dart

@@ -0,0 +1,75 @@
+import 'package:flutter/material.dart';
+
+import '../services/theme_service.dart';
+import 'app_colors.dart';
+
+/// InheritedWidget providing runtime theme colors
+///
+/// Wraps the app and provides semantic color getters that resolve
+/// to dark or bright variants based on ThemeService state.
+///
+/// Usage: AppTheme.of(context).background
+class AppTheme extends InheritedWidget {
+  final bool isDarkMode;
+
+  const AppTheme({
+    super.key,
+    required this.isDarkMode,
+    required super.child,
+  });
+
+  /// Get the nearest AppTheme from context
+  static AppTheme of(BuildContext context) {
+    final theme = context.dependOnInheritedWidgetOfExactType<AppTheme>();
+    assert(theme != null, 'No AppTheme found in context');
+    return theme!;
+  }
+
+  // Semantic color getters - pick dark or bright based on mode
+  Color get background => isDarkMode ? AppColors.darkBackground : AppColors.brightBackground;
+  Color get foreground => isDarkMode ? AppColors.darkForeground : AppColors.brightForeground;
+  Color get highlight => isDarkMode ? AppColors.darkHighlight : AppColors.brightHighlight;
+  Color get subdued => isDarkMode ? AppColors.darkSubdued : AppColors.brightSubdued;
+
+  @override
+  bool updateShouldNotify(AppTheme oldWidget) => isDarkMode != oldWidget.isDarkMode;
+}
+
+/// Wrapper widget that manages AppTheme state
+///
+/// Listens to ThemeService and rebuilds when theme changes.
+/// Place this at the root of your widget tree.
+class AppThemeProvider extends StatefulWidget {
+  final Widget child;
+
+  const AppThemeProvider({super.key, required this.child});
+
+  @override
+  State<AppThemeProvider> createState() => _AppThemeProviderState();
+}
+
+class _AppThemeProviderState extends State<AppThemeProvider> {
+  @override
+  void initState() {
+    super.initState();
+    ThemeService.instance.addListener(_onThemeChanged);
+  }
+
+  @override
+  void dispose() {
+    ThemeService.instance.removeListener(_onThemeChanged);
+    super.dispose();
+  }
+
+  void _onThemeChanged() {
+    setState(() {});
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return AppTheme(
+      isDarkMode: ThemeService.instance.isDarkMode,
+      child: widget.child,
+    );
+  }
+}