feat：参照研听的基础工程

lib/common/domain/metal_type.dart

@@ -0,0 +1,14 @@
+import 'package:flutter/material.dart';
+
+enum MetalType {
+  gold('gold', '黄金', '金', Color(0xFFB5862A)),
+  platinum('platinum', '铂金', '铂', Color(0xFF7D8792)),
+  silver('silver', '白银', '银', Color(0xFF9DA3AA));
+
+  const MetalType(this.id, this.label, this.shortLabel, this.color);
+
+  final String id;
+  final String label;
+  final String shortLabel;
+  final Color color;
+}

lib/common/domain/money.dart

@@ -0,0 +1,11 @@
+String formatCny(num value) {
+  final fixed = value.toStringAsFixed(2);
+  final parts = fixed.split('.');
+  final whole = parts.first.replaceAllMapped(
+    RegExp(r'(\d)(?=(\d{3})+(?!\d))'),
+    (match) => '${match[1]},',
+  );
+  return '¥$whole.${parts.last}';
+}
+
+String formatGram(num value) => '${value.toStringAsFixed(2)}g';