feat: Add XtremFlow color palette for light/dark themes and initial Flutter web HTML with a themed loading screen.

lib/core/providers/theme_provider.dart

@@ -0,0 +1,111 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+
+/// Theme mode preference options
+enum AppThemeMode {
+  system, // Follow system preference
+  light,  // Force light mode
+  dark,   // Force dark mode
+}
+
+/// Keys for SharedPreferences storage
+class _ThemeKeys {
+  static const String themeMode = 'app_theme_mode';
+}
+
+/// Theme state containing current mode
+class ThemeState {
+  final AppThemeMode appThemeMode;
+  final ThemeMode themeMode;
+
+  const ThemeState({
+    this.appThemeMode = AppThemeMode.dark,
+    this.themeMode = ThemeMode.dark,
+  });
+
+  ThemeState copyWith({
+    AppThemeMode? appThemeMode,
+    ThemeMode? themeMode,
+  }) {
+    return ThemeState(
+      appThemeMode: appThemeMode ?? this.appThemeMode,
+      themeMode: themeMode ?? this.themeMode,
+    );
+  }
+}
+
+/// Theme provider for managing light/dark mode with persistence
+class ThemeNotifier extends StateNotifier<ThemeState> {
+  ThemeNotifier() : super(const ThemeState()) {
+    _loadTheme();
+  }
+
+  /// Load saved theme preference from SharedPreferences
+  Future<void> _loadTheme() async {
+    try {
+      final prefs = await SharedPreferences.getInstance();
+      final savedMode = prefs.getString(_ThemeKeys.themeMode);
+      
+      if (savedMode != null) {
+        final appMode = AppThemeMode.values.firstWhere(
+          (e) => e.name == savedMode,
+          orElse: () => AppThemeMode.dark,
+        );
+        state = state.copyWith(
+          appThemeMode: appMode,
+          themeMode: _mapToThemeMode(appMode),
+        );
+      }
+    } catch (e) {
+      debugPrint('Error loading theme: $e');
+    }
+  }
+
+  /// Set theme mode and persist to SharedPreferences
+  Future<void> setThemeMode(AppThemeMode mode) async {
+    state = state.copyWith(
+      appThemeMode: mode,
+      themeMode: _mapToThemeMode(mode),
+    );
+    
+    try {
+      final prefs = await SharedPreferences.getInstance();
+      await prefs.setString(_ThemeKeys.themeMode, mode.name);
+    } catch (e) {
+      debugPrint('Error saving theme: $e');
+    }
+  }
+
+  /// Quick toggle between light and dark (skip system)
+  Future<void> toggleTheme() async {
+    final newMode = state.appThemeMode == AppThemeMode.dark
+        ? AppThemeMode.light
+        : AppThemeMode.dark;
+    await setThemeMode(newMode);
+  }
+
+  /// Check if currently in dark mode
+  bool get isDarkMode {
+    return state.themeMode == ThemeMode.dark ||
+        (state.themeMode == ThemeMode.system && 
+         WidgetsBinding.instance.platformDispatcher.platformBrightness == Brightness.dark);
+  }
+
+  /// Map AppThemeMode to Flutter's ThemeMode
+  ThemeMode _mapToThemeMode(AppThemeMode mode) {
+    switch (mode) {
+      case AppThemeMode.system:
+        return ThemeMode.system;
+      case AppThemeMode.light:
+        return ThemeMode.light;
+      case AppThemeMode.dark:
+        return ThemeMode.dark;
+    }
+  }
+}
+
+/// Provider for theme state
+final themeProvider = StateNotifierProvider<ThemeNotifier, ThemeState>((ref) {
+  return ThemeNotifier();
+});