feat: refactor flower.utils to sub package, added some sync api in package, added plate_order sync result model but relation of plate_order was not query (do it next step)

business/services.py

@@ -1723,8 +1723,10 @@ def _to_decimal(value, field_name: str) -> Decimal:
 
 def _ensure_non_zero_amount(value, field_name: str) -> Decimal:
     amount = _to_decimal(value, field_name)
-    if amount == 0:
-        raise ValueError(f'{field_name} 不能为 0')
+    # 金额类字段统一要求 > 0（amount ≤ 0 视为非法）
+    if amount <= 0:
+        # 与 API 文档/测试约定保持一致
+        raise ValueError(f'{field_name} 必须大于 0')
     return amount