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/core/services/theme_service.dart

@@ -0,0 +1,95 @@
+import 'package:shared_preferences/shared_preferences.dart';
+import 'package:flutter/material.dart';
+import '../utils/logger.dart';
+
+/// Service for managing app theme preferences
+class ThemeService {
+  static const String _themeKey = 'app_theme_mode';
+  static const ThemeMode _defaultTheme = ThemeMode.light;
+
+  /// Get current theme mode from storage
+  static Future<ThemeMode> getThemeMode() async {
+    try {
+      final prefs = await SharedPreferences.getInstance();
+      final themeString = prefs.getString(_themeKey);
+
+      if (themeString == null) {
+        return _defaultTheme;
+      }
+
+      switch (themeString) {
+        case 'ThemeMode.light':
+          return ThemeMode.light;
+        case 'ThemeMode.dark':
+          return ThemeMode.dark;
+        case 'ThemeMode.system':
+          return ThemeMode.system;
+        default:
+          return _defaultTheme;
+      }
+    } catch (e) {
+      Logger.error('Error getting theme mode: $e');
+      return _defaultTheme;
+    }
+  }
+
+  /// Save theme mode to storage
+  static Future<void> setThemeMode(ThemeMode themeMode) async {
+    try {
+      final prefs = await SharedPreferences.getInstance();
+      await prefs.setString(_themeKey, themeMode.toString());
+      Logger.info('Theme mode saved: ${themeMode.toString()}');
+    } catch (e) {
+      Logger.error('Error saving theme mode: $e');
+    }
+  }
+
+  /// Get theme mode from storage (for future use)
+  static Future<ThemeMode> getStoredThemeMode() async {
+    try {
+      final prefs = await SharedPreferences.getInstance();
+      final themeString = prefs.getString(_themeKey);
+
+      if (themeString == null) {
+        return _defaultTheme;
+      }
+
+      switch (themeString) {
+        case 'ThemeMode.light':
+          return ThemeMode.light;
+        case 'ThemeMode.dark':
+          return ThemeMode.dark;
+        case 'ThemeMode.system':
+          return ThemeMode.system;
+        default:
+          return _defaultTheme;
+      }
+    } catch (e) {
+      Logger.error('Error getting stored theme mode: $e');
+      return _defaultTheme;
+    }
+  }
+
+  /// Check if dark mode is available (for future settings)
+  static bool isDarkModeAvailable() {
+    // Dark mode is now available
+    return true;
+  }
+
+  /// Get theme mode string for display
+  static String getThemeModeString(ThemeMode themeMode) {
+    switch (themeMode) {
+      case ThemeMode.light:
+        return 'Light Mode';
+      case ThemeMode.dark:
+        return 'Dark Mode';
+      case ThemeMode.system:
+        return 'System Default';
+    }
+  }
+
+  /// Reset theme to default
+  static Future<void> resetTheme() async {
+    await setThemeMode(_defaultTheme);
+  }
+}