fix：增加图片选择和拍照功能

lib/features/assets/data/asset_models.dart

@@ -1,5 +1,58 @@
 import '../../../common/domain/metal_type.dart';
 
+class AssetImage {
+  const AssetImage({
+    required this.localId,
+    required this.localPath,
+    required this.createdAt,
+    this.remoteUrl,
+    this.thumbnailUrl,
+  });
+
+  final String localId;
+  final String localPath;
+  final String? remoteUrl;
+  final String? thumbnailUrl;
+  final DateTime createdAt;
+
+  AssetImage copyWith({
+    String? localId,
+    String? localPath,
+    String? remoteUrl,
+    String? thumbnailUrl,
+    DateTime? createdAt,
+  }) {
+    return AssetImage(
+      localId: localId ?? this.localId,
+      localPath: localPath ?? this.localPath,
+      remoteUrl: remoteUrl ?? this.remoteUrl,
+      thumbnailUrl: thumbnailUrl ?? this.thumbnailUrl,
+      createdAt: createdAt ?? this.createdAt,
+    );
+  }
+
+  Map<String, dynamic> toJson() {
+    return {
+      'localId': localId,
+      'localPath': localPath,
+      'remoteUrl': remoteUrl,
+      'thumbnailUrl': thumbnailUrl,
+      'createdAt': createdAt.toIso8601String(),
+    };
+  }
+
+  factory AssetImage.fromJson(Map<String, dynamic> json) {
+    return AssetImage(
+      localId: json['localId'] as String? ?? '',
+      localPath: json['localPath'] as String? ?? '',
+      remoteUrl: json['remoteUrl'] as String?,
+      thumbnailUrl: json['thumbnailUrl'] as String?,
+      createdAt: DateTime.tryParse(json['createdAt'] as String? ?? '') ??
+          DateTime.fromMillisecondsSinceEpoch(0),
+    );
+  }
+}
+
 enum AssetCategory {
   bar('金条'),
   necklace('项链'),
@@ -28,6 +81,7 @@ class GoldAssetHolding {
     required this.weightGram,
     required this.createdAt,
     required this.updatedAt,
+    this.images = const [],
     this.costAmount,
     this.purchaseDate,
     this.channel,
@@ -42,6 +96,7 @@ class GoldAssetHolding {
   final double purity;
   final String purityLabel;
   final double weightGram;
+  final List<AssetImage> images;
   final double? costAmount;
   final DateTime? purchaseDate;
   final String? channel;
@@ -50,7 +105,92 @@ class GoldAssetHolding {
   final DateTime updatedAt;
   final HoldingStatus status;
 
+  GoldAssetHolding copyWith({
+    String? id,
+    String? name,
+    MetalType? metal,
+    AssetCategory? category,
+    double? purity,
+    String? purityLabel,
+    double? weightGram,
+    List<AssetImage>? images,
+    double? costAmount,
+    DateTime? purchaseDate,
+    String? channel,
+    String? note,
+    DateTime? createdAt,
+    DateTime? updatedAt,
+    HoldingStatus? status,
+  }) {
+    return GoldAssetHolding(
+      id: id ?? this.id,
+      name: name ?? this.name,
+      metal: metal ?? this.metal,
+      category: category ?? this.category,
+      purity: purity ?? this.purity,
+      purityLabel: purityLabel ?? this.purityLabel,
+      weightGram: weightGram ?? this.weightGram,
+      images: images ?? this.images,
+      costAmount: costAmount ?? this.costAmount,
+      purchaseDate: purchaseDate ?? this.purchaseDate,
+      channel: channel ?? this.channel,
+      note: note ?? this.note,
+      createdAt: createdAt ?? this.createdAt,
+      updatedAt: updatedAt ?? this.updatedAt,
+      status: status ?? this.status,
+    );
+  }
+
   double materialValue(double spotPrice) => weightGram * purity * spotPrice;
+
+  Map<String, dynamic> toJson() {
+    return {
+      'id': id,
+      'name': name,
+      'metalId': metal.id,
+      'categoryId': category.name,
+      'purity': purity,
+      'purityLabel': purityLabel,
+      'weightGram': weightGram,
+      'images': images.map((item) => item.toJson()).toList(growable: false),
+      'costAmount': costAmount,
+      'purchaseDate': purchaseDate?.toIso8601String(),
+      'channel': channel,
+      'note': note,
+      'createdAt': createdAt.toIso8601String(),
+      'updatedAt': updatedAt.toIso8601String(),
+      'status': status.name,
+    };
+  }
+
+  factory GoldAssetHolding.fromJson(Map<String, dynamic> json) {
+    final rawImages = json['images'];
+    return GoldAssetHolding(
+      id: json['id'] as String? ?? '',
+      name: json['name'] as String? ?? '',
+      metal: _metalFromId(json['metalId'] as String?),
+      category: _categoryFromId(json['categoryId'] as String?),
+      purity: (json['purity'] as num?)?.toDouble() ?? 1,
+      purityLabel: json['purityLabel'] as String? ?? '',
+      weightGram: (json['weightGram'] as num?)?.toDouble() ?? 0,
+      images: rawImages is List
+          ? [
+              for (final raw in rawImages)
+                if (raw is Map)
+                  AssetImage.fromJson(Map<String, dynamic>.from(raw)),
+            ]
+          : const [],
+      costAmount: (json['costAmount'] as num?)?.toDouble(),
+      purchaseDate: DateTime.tryParse(json['purchaseDate'] as String? ?? ''),
+      channel: json['channel'] as String?,
+      note: json['note'] as String?,
+      createdAt: DateTime.tryParse(json['createdAt'] as String? ?? '') ??
+          DateTime.fromMillisecondsSinceEpoch(0),
+      updatedAt: DateTime.tryParse(json['updatedAt'] as String? ?? '') ??
+          DateTime.fromMillisecondsSinceEpoch(0),
+      status: _statusFromName(json['status'] as String?),
+    );
+  }
 }
 
 class HoldingValuation {
@@ -100,3 +240,26 @@ class PortfolioSummary {
   final List<MetalBreakdown> breakdowns;
   final List<HoldingValuation> holdings;
 }
+
+MetalType _metalFromId(String? id) {
+  return switch (id) {
+    'gold' => MetalType.gold,
+    'platinum' => MetalType.platinum,
+    'silver' => MetalType.silver,
+    _ => MetalType.gold,
+  };
+}
+
+AssetCategory _categoryFromId(String? id) {
+  return AssetCategory.values.firstWhere(
+    (item) => item.name == id,
+    orElse: () => AssetCategory.bar,
+  );
+}
+
+HoldingStatus _statusFromName(String? value) {
+  return HoldingStatus.values.firstWhere(
+    (item) => item.name == value,
+    orElse: () => HoldingStatus.active,
+  );
+}