Initial scaffold: FocusFlow shared Dart package

Models (Task, Streak, StreakEntry, Reward, User, TimeEstimate, CoworkingRoom, ApiResponse),
enums (EnergyLevel, TaskStatus, RewardType, RewardStyle),
constants (ApiConstants, ErrorCodes, AppLimits), validators, and generated .g.dart files.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

lib/src/models/api_response.g.dart

@@ -0,0 +1,71 @@
+// GENERATED CODE - DO NOT MODIFY BY HAND
+
+part of 'api_response.dart';
+
+// **************************************************************************
+// JsonSerializableGenerator
+// **************************************************************************
+
+ApiResponse<T> _$ApiResponseFromJson<T>(
+  Map<String, dynamic> json,
+  T Function(Object? json) fromJsonT,
+) => ApiResponse<T>(
+  status: json['status'] as String,
+  data: _$nullableGenericFromJson(json['data'], fromJsonT),
+  error:
+      json['error'] == null
+          ? null
+          : ApiError.fromJson(json['error'] as Map<String, dynamic>),
+  meta:
+      json['meta'] == null
+          ? null
+          : PaginationMeta.fromJson(json['meta'] as Map<String, dynamic>),
+);
+
+Map<String, dynamic> _$ApiResponseToJson<T>(
+  ApiResponse<T> instance,
+  Object? Function(T value) toJsonT,
+) => <String, dynamic>{
+  'status': instance.status,
+  'data': _$nullableGenericToJson(instance.data, toJsonT),
+  'error': instance.error,
+  'meta': instance.meta,
+};
+
+T? _$nullableGenericFromJson<T>(
+  Object? input,
+  T Function(Object? json) fromJson,
+) => input == null ? null : fromJson(input);
+
+Object? _$nullableGenericToJson<T>(
+  T? input,
+  Object? Function(T value) toJson,
+) => input == null ? null : toJson(input);
+
+ApiError _$ApiErrorFromJson(Map<String, dynamic> json) => ApiError(
+  code: json['code'] as String,
+  message: json['message'] as String,
+  details: json['details'],
+);
+
+Map<String, dynamic> _$ApiErrorToJson(ApiError instance) => <String, dynamic>{
+  'code': instance.code,
+  'message': instance.message,
+  'details': instance.details,
+};
+
+PaginationMeta _$PaginationMetaFromJson(Map<String, dynamic> json) =>
+    PaginationMeta(
+      page: (json['page'] as num).toInt(),
+      limit: (json['limit'] as num).toInt(),
+      total: (json['total'] as num).toInt(),
+      hasMore: json['hasMore'] as bool,
+    );
+
+Map<String, dynamic> _$PaginationMetaToJson(PaginationMeta instance) =>
+    <String, dynamic>{
+      'page': instance.page,
+      'limit': instance.limit,
+      'total': instance.total,
+      'hasMore': instance.hasMore,
+    };