feat: usar a cor escolhida tal e qual e opcao de suavizar

- TatuPalette.scheme aceita softenPrimary e passa a usar a seed como primary, onPrimary por contraste e surfaceTint, em vez da paleta tonal do Material 3
- nova opcao AppSettings.softenThemeColor (default false, ou seja cor exacta)
- interruptor 'Suavizar cor do tema' em Configuracoes > Aparencia, com l10n en/pt
- a opcao e sincronizada via account data (soften_theme_color) e mantida localmente como fallback, tal como a cor do tema
- setApplicationAccountColor e updateApplicationAccountConfig preservam o novo campo
- um unico sync de account data actualiza cor e opcao
- testes de serializacao e round-trip para o novo campo

lib/utils/account_config.dart

@@ -28,6 +28,8 @@ extension ApplicationAccountConfigExtension on Client {
             config.wallpaperOpacity ?? currentConfig.wallpaperOpacity,
         wallpaperBlur: config.wallpaperBlur ?? currentConfig.wallpaperBlur,
         primaryColor: config.primaryColor ?? currentConfig.primaryColor,
+        softenThemeColor:
+            config.softenThemeColor ?? currentConfig.softenThemeColor,
       ).toJson(),
     );
   }
@@ -40,6 +42,20 @@ extension ApplicationAccountConfigExtension on Client {
         wallpaperOpacity: currentConfig.wallpaperOpacity,
         wallpaperBlur: currentConfig.wallpaperBlur,
         primaryColor: primaryColor,
+        softenThemeColor: currentConfig.softenThemeColor,
+      ),
+    );
+  }
+
+  Future<void> setApplicationAccountSoftenThemeColor(bool soften) {
+    final currentConfig = applicationAccountConfig;
+    return setApplicationAccountConfig(
+      ApplicationAccountConfig(
+        wallpaperUrl: currentConfig.wallpaperUrl,
+        wallpaperOpacity: currentConfig.wallpaperOpacity,
+        wallpaperBlur: currentConfig.wallpaperBlur,
+        primaryColor: currentConfig.primaryColor,
+        softenThemeColor: soften,
       ),
     );
   }
@@ -50,12 +66,14 @@ class ApplicationAccountConfig {
   final double? wallpaperOpacity;
   final double? wallpaperBlur;
   final int? primaryColor;
+  final bool? softenThemeColor;
 
   const ApplicationAccountConfig({
     this.wallpaperUrl,
     this.wallpaperOpacity,
     this.wallpaperBlur,
     this.primaryColor,
+    this.softenThemeColor,
   });
 
   static double _sanitizedOpacity(double? opacity) {
@@ -74,6 +92,7 @@ class ApplicationAccountConfig {
         ),
         wallpaperBlur: json.tryGet<double>('wallpaper_blur'),
         primaryColor: json.tryGet<int>('primary_color'),
+        softenThemeColor: json.tryGet<bool>('soften_theme_color'),
       );
 
   Map<String, dynamic> toJson() => {
@@ -81,5 +100,6 @@ class ApplicationAccountConfig {
     'wallpaper_opacity': wallpaperOpacity,
     'wallpaper_blur': wallpaperBlur,
     'primary_color': primaryColor,
+    'soften_theme_color': softenThemeColor,
   };
 }