已完成用户APP首期功能开发

交付用户端首期页面、配套接口、后台资源及测试文档。用户APP构建、静态分析和三个管理后台构建通过；完整测试仍有2项失败，后端模型注释检查未通过，详见交付记录。

apps/user_app/lib/domain/models/usage_statistics.dart

@@ -0,0 +1,78 @@
+// 功能描述：定义用气统计的服务端事实模型；版本：1.0.0。
+
+class UsagePoint {
+  const UsagePoint({required this.date, required this.usage});
+  final DateTime date;
+  final double usage;
+
+  factory UsagePoint.fromJson(Map<String, Object?> json) => UsagePoint(
+    date: DateTime.parse(json['date'] as String),
+    usage: (json['usage'] as num).toDouble(),
+  );
+}
+
+class UsageComposition {
+  const UsageComposition({required this.breakfast, required this.lunch, required this.dinner});
+  final double breakfast, lunch, dinner;
+
+  factory UsageComposition.fromJson(Map<String, Object?> json) => UsageComposition(
+    breakfast: (json['breakfast'] as num? ?? 0).toDouble(),
+    lunch: (json['lunch'] as num? ?? 0).toDouble(),
+    dinner: (json['dinner'] as num? ?? 0).toDouble(),
+  );
+}
+
+class UsageStatistics {
+  const UsageStatistics({
+    required this.available,
+    required this.deviceIdentity,
+    required this.deviceName,
+    required this.deviceCode,
+    required this.period,
+    required this.periodStart,
+    required this.periodEnd,
+    required this.unit,
+    required this.points,
+    required this.totalUsage,
+    required this.averageUsage,
+    required this.composition,
+    required this.source,
+    required this.calcVersion,
+    required this.updatedAt,
+    required this.unavailableReason,
+  });
+
+  final bool available;
+  final String deviceIdentity, deviceName, deviceCode, period, unit;
+  final DateTime periodStart, periodEnd;
+  final List<UsagePoint> points;
+  final double totalUsage, averageUsage;
+  final UsageComposition composition;
+  final String source, calcVersion, unavailableReason;
+  final DateTime? updatedAt;
+
+  factory UsageStatistics.fromJson(Map<String, Object?> json) {
+    final device = json['device'] as Map<String, Object?>? ?? const {};
+    final composition = json['composition'] as Map<String, Object?>? ?? const {};
+    return UsageStatistics(
+      available: json['available'] == true,
+      deviceIdentity: device['identity'] as String? ?? '',
+      deviceName: device['name'] as String? ?? '',
+      deviceCode: device['code'] as String? ?? '',
+      period: json['period'] as String? ?? 'month',
+      periodStart: DateTime.parse(json['period_start'] as String),
+      periodEnd: DateTime.parse(json['period_end'] as String),
+      unit: json['unit'] as String? ?? 'kg',
+      points: (json['points'] as List<Object?>? ?? const [])
+          .map((item) => UsagePoint.fromJson(item as Map<String, Object?>))
+          .toList(),
+      totalUsage: (json['total_usage'] as num? ?? 0).toDouble(),
+      averageUsage: (json['average_usage'] as num? ?? 0).toDouble(),
+      composition: UsageComposition.fromJson(composition),
+      source: json['source'] as String? ?? '',
+      calcVersion: json['calc_version'] as String? ?? '',
+      updatedAt: DateTime.tryParse(json['updated_at']?.toString() ?? '')?.toLocal(),
+      unavailableReason: json['unavailable_reason'] as String? ?? '',
+    );
+  }
+}