feat: 长辈模式（大字大按钮 + 偏好按账号隔离）+ 语音输入（按住说话 + 实时转写 + 后端代理 DashScope ASR + 患者端专用）+ 健康仪表盘背景渐变

health_app/lib/providers/elder_mode_provider.dart

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+import 'dart:convert';
+
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+
+import 'auth_provider.dart';
+
+class ElderModePreferences {
+  final bool enabled;
+  final bool largeTextEnabled;
+  final bool voiceInputEnabled;
+
+  const ElderModePreferences({
+    this.enabled = false,
+    this.largeTextEnabled = true,
+    this.voiceInputEnabled = true,
+  });
+
+  ElderModePreferences copyWith({
+    bool? enabled,
+    bool? largeTextEnabled,
+    bool? voiceInputEnabled,
+  }) {
+    return ElderModePreferences(
+      enabled: enabled ?? this.enabled,
+      largeTextEnabled: largeTextEnabled ?? this.largeTextEnabled,
+      voiceInputEnabled: voiceInputEnabled ?? this.voiceInputEnabled,
+    );
+  }
+
+  Map<String, dynamic> toJson() => {
+    'schemaVersion': 1,
+    'enabled': enabled,
+    'largeTextEnabled': largeTextEnabled,
+    'voiceInputEnabled': voiceInputEnabled,
+  };
+
+  factory ElderModePreferences.fromJson(Map<String, dynamic> json) {
+    return ElderModePreferences(
+      enabled: json['enabled'] == true,
+      largeTextEnabled: json['largeTextEnabled'] != false,
+      voiceInputEnabled: json['voiceInputEnabled'] != false,
+    );
+  }
+}
+
+class ElderModeState {
+  final ElderModePreferences preferences;
+  final bool isLoaded;
+  final bool isSaving;
+  final String? error;
+
+  const ElderModeState({
+    this.preferences = const ElderModePreferences(),
+    this.isLoaded = false,
+    this.isSaving = false,
+    this.error,
+  });
+
+  bool get isEnabled => preferences.enabled;
+  bool get useLargeText => isEnabled && preferences.largeTextEnabled;
+
+  ElderModeState copyWith({
+    ElderModePreferences? preferences,
+    bool? isLoaded,
+    bool? isSaving,
+    String? error,
+    bool clearError = false,
+  }) {
+    return ElderModeState(
+      preferences: preferences ?? this.preferences,
+      isLoaded: isLoaded ?? this.isLoaded,
+      isSaving: isSaving ?? this.isSaving,
+      error: clearError ? null : error ?? this.error,
+    );
+  }
+}
+
+final elderModeProvider = NotifierProvider<ElderModeNotifier, ElderModeState>(
+  ElderModeNotifier.new,
+);
+
+class ElderModeNotifier extends Notifier<ElderModeState> {
+  static const _storageKeyPrefix = 'accessibility_preferences_v1:user_';
+  String? _currentUserId;
+
+  @override
+  ElderModeState build() {
+    final userId = ref.watch(
+      authProvider.select((state) => state.user?.id),
+    );
+    _currentUserId = userId;
+    if (userId == null || userId.isEmpty) {
+      return const ElderModeState(isLoaded: true);
+    }
+    Future<void>.microtask(_load);
+    return const ElderModeState();
+  }
+
+  String get _storageKey => '$_storageKeyPrefix$_currentUserId';
+
+  Future<void> _load() async {
+    if (_currentUserId == null || _currentUserId!.isEmpty) return;
+    try {
+      final raw = await ref.read(localDbProvider).read(_storageKey);
+      if (raw == null || raw.trim().isEmpty) {
+        state = state.copyWith(isLoaded: true, clearError: true);
+        return;
+      }
+      final decoded = jsonDecode(raw);
+      if (decoded is! Map) throw const FormatException('invalid preferences');
+      state = state.copyWith(
+        preferences: ElderModePreferences.fromJson(
+          Map<String, dynamic>.from(decoded),
+        ),
+        isLoaded: true,
+        clearError: true,
+      );
+    } catch (_) {
+      state = state.copyWith(isLoaded: true, error: '长辈模式设置读取失败，已使用默认设置');
+    }
+  }
+
+  Future<bool> enable() =>
+      _save(state.preferences.copyWith(enabled: true, largeTextEnabled: true));
+
+  Future<bool> disable() => _save(state.preferences.copyWith(enabled: false));
+
+  Future<bool> setLargeTextEnabled(bool enabled) =>
+      _save(state.preferences.copyWith(largeTextEnabled: enabled));
+
+  Future<bool> setVoiceInputEnabled(bool enabled) =>
+      _save(state.preferences.copyWith(voiceInputEnabled: enabled));
+
+  Future<bool> _save(ElderModePreferences next) async {
+    if (_currentUserId == null || _currentUserId!.isEmpty) {
+      state = state.copyWith(
+        isLoaded: true,
+        error: '请先登录后再调整长辈模式',
+      );
+      return false;
+    }
+    final previous = state.preferences;
+    state = state.copyWith(
+      preferences: next,
+      isLoaded: true,
+      isSaving: true,
+      clearError: true,
+    );
+    try {
+      await ref.read(localDbProvider).write(_storageKey, jsonEncode(next));
+      state = state.copyWith(isSaving: false, clearError: true);
+      return true;
+    } catch (_) {
+      state = state.copyWith(
+        preferences: previous,
+        isSaving: false,
+        error: '保存失败，请稍后重试',
+      );
+      return false;
+    }
+  }
+}