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/widgets/theme_builder.dart

@@ -7,6 +7,7 @@ import 'dart:async';
 
 import 'package:collection/collection.dart';
 import 'package:dynamic_color/dynamic_color.dart';
+import 'package:tatchat/config/setting_keys.dart';
 import 'package:tatchat/utils/account_config.dart';
 import 'package:tatchat/utils/color_value.dart';
 import 'package:material_ui/material_ui.dart';
@@ -43,6 +44,9 @@ class ThemeController extends State<ThemeBuilder> {
   Color? _primaryColor;
   Color? _localPrimaryColor;
   Color? _accountPrimaryColor;
+  bool _softenPrimaryColor = false;
+  bool _localSoftenPrimaryColor = false;
+  bool? _accountSoftenPrimaryColor;
   Client? _accountClient;
   StreamSubscription<SyncUpdate>? _accountClientSubscription;
   int _accountClientGeneration = 0;
@@ -51,6 +55,8 @@ class ThemeController extends State<ThemeBuilder> {
 
   Color? get primaryColor => _primaryColor;
 
+  bool get softenPrimaryColor => _softenPrimaryColor;
+
   static ThemeController of(BuildContext context) =>
       Provider.of<ThemeController>(context, listen: false);
 
@@ -63,6 +69,15 @@ class ThemeController extends State<ThemeBuilder> {
     });
   }
 
+  void _updateSoftenPrimaryColor() {
+    if (!mounted) return;
+    final newValue = _accountSoftenPrimaryColor ?? _localSoftenPrimaryColor;
+    if (newValue == _softenPrimaryColor) return;
+    setState(() {
+      _softenPrimaryColor = newValue;
+    });
+  }
+
   Future<void> _loadData(_) async {
     final preferences = _sharedPreferences ??=
         await SharedPreferences.getInstance();
@@ -76,8 +91,10 @@ class ThemeController extends State<ThemeBuilder> {
         (value) => value.name == rawThemeMode,
       );
       _localPrimaryColor = rawColor == null ? null : Color(rawColor);
+      _localSoftenPrimaryColor = AppSettings.softenThemeColor.value;
     });
     _updatePrimaryColor();
+    _updateSoftenPrimaryColor();
   }
 
   Future<void> setThemeMode(ThemeMode newThemeMode) async {
@@ -108,6 +125,23 @@ class ThemeController extends State<ThemeBuilder> {
     }
   }
 
+  Future<void> setSoftenPrimaryColor(bool soften) async {
+    await AppSettings.softenThemeColor.setItem(soften);
+    if (!mounted) return;
+    setState(() {
+      _localSoftenPrimaryColor = soften;
+      _accountSoftenPrimaryColor = soften;
+      _softenPrimaryColor = soften;
+    });
+    final client = _accountClient;
+    if (client == null) return;
+    try {
+      await client.setApplicationAccountSoftenThemeColor(soften);
+    } catch (err) {
+      Logs().e('TatuChat: failed to sync soften theme color', err);
+    }
+  }
+
   void setAccountClient(Client? client) {
     if (!mounted) return;
     final generation = ++_accountClientGeneration;
@@ -115,10 +149,12 @@ class ThemeController extends State<ThemeBuilder> {
     _accountClientSubscription = null;
     _accountClient = client;
     _accountPrimaryColor = null;
+    _accountSoftenPrimaryColor = null;
     _updatePrimaryColor();
+    _updateSoftenPrimaryColor();
     if (client == null) return;
 
-    unawaited(_loadAccountClientColor(client, generation));
+    unawaited(_loadAccountClientConfig(client, generation));
     _accountClientSubscription = client.onSync.stream
         .where(
           (sync) =>
@@ -129,10 +165,10 @@ class ThemeController extends State<ThemeBuilder> {
               ) ??
               false,
         )
-        .listen((_) => _applyAccountClientColor(client, generation));
+        .listen((_) => _applyAccountClientConfig(client, generation));
   }
 
-  Future<void> _loadAccountClientColor(Client client, int generation) async {
+  Future<void> _loadAccountClientConfig(Client client, int generation) async {
     final accountDataLoading = client.accountDataLoading;
     if (accountDataLoading != null) {
       try {
@@ -144,18 +180,21 @@ class ThemeController extends State<ThemeBuilder> {
         !identical(_accountClient, client)) {
       return;
     }
-    _applyAccountClientColor(client, generation);
+    _applyAccountClientConfig(client, generation);
   }
 
-  void _applyAccountClientColor(Client client, int generation) {
+  void _applyAccountClientConfig(Client client, int generation) {
     if (!mounted ||
         generation != _accountClientGeneration ||
         !identical(_accountClient, client)) {
       return;
     }
-    final primaryColor = client.applicationAccountConfig.primaryColor;
+    final config = client.applicationAccountConfig;
+    final primaryColor = config.primaryColor;
     _accountPrimaryColor = primaryColor == null ? null : Color(primaryColor);
+    _accountSoftenPrimaryColor = config.softenThemeColor;
     _updatePrimaryColor();
+    _updateSoftenPrimaryColor();
   }
 
   @override