Settings, correção de light/darkmode do dispositivo (e adição da escolha entre modos nas settings) e correção do tipo de letra no textfield do chatbot

lib/features/settings/presentation/providers/settings_provider.dart

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+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import '../../../../core/services/theme_service.dart';
+
+/// Settings state
+class SettingsState {
+  final ThemeMode themeMode;
+  final bool isDarkModeAvailable;
+  final bool isLoading;
+
+  const SettingsState({
+    required this.themeMode,
+    required this.isDarkModeAvailable,
+    this.isLoading = false,
+  });
+
+  SettingsState copyWith({
+    ThemeMode? themeMode,
+    bool? isDarkModeAvailable,
+    bool? isLoading,
+  }) {
+    return SettingsState(
+      themeMode: themeMode ?? this.themeMode,
+      isDarkModeAvailable: isDarkModeAvailable ?? this.isDarkModeAvailable,
+      isLoading: isLoading ?? this.isLoading,
+    );
+  }
+}
+
+/// Settings notifier
+class SettingsNotifier extends StateNotifier<SettingsState> {
+  SettingsNotifier()
+    : super(
+        SettingsState(
+          themeMode: ThemeService.getThemeMode(),
+          isDarkModeAvailable: ThemeService.isDarkModeAvailable(),
+        ),
+      );
+
+  /// Set theme mode
+  Future<void> setThemeMode(ThemeMode themeMode) async {
+    state = state.copyWith(isLoading: true);
+    await ThemeService.setThemeMode(themeMode);
+    state = state.copyWith(themeMode: themeMode, isLoading: false);
+  }
+
+  /// Load settings from storage
+  Future<void> loadSettings() async {
+    state = state.copyWith(isLoading: true);
+    final themeMode = await ThemeService.getStoredThemeMode();
+    final isDarkModeAvailable = ThemeService.isDarkModeAvailable();
+    state = state.copyWith(
+      themeMode: themeMode,
+      isDarkModeAvailable: isDarkModeAvailable,
+      isLoading: false,
+    );
+  }
+
+  /// Reset settings to default
+  Future<void> resetSettings() async {
+    state = state.copyWith(isLoading: true);
+    await ThemeService.resetTheme();
+    state = state.copyWith(
+      themeMode: ThemeService.getThemeMode(),
+      isLoading: false,
+    );
+  }
+}
+
+/// Settings provider
+final settingsProvider = StateNotifierProvider<SettingsNotifier, SettingsState>(
+  (ref) => SettingsNotifier(),
+);
+
+/// Theme mode provider (convenience)
+final themeModeProvider = Provider<ThemeMode>(
+  (ref) => ref.watch(settingsProvider).themeMode,
+);
+
+/// Dark mode available provider (convenience)
+final isDarkModeAvailableProvider = Provider<bool>(
+  (ref) => ref.watch(settingsProvider).isDarkModeAvailable,
+);