feat(opc): 添加S7直写支持并更新字段映射格式

- 在OpcConfig模型中新增S7终端、机架和槽位配置
- 实现S7直写功能，替代原有的OPC写入方式
- 更新前端字段映射占位符为S7地址格式
- 修改焊接完成信号触发条件说明
- 添加S7 INT32读取功能用于数据版本控制

backend/main.py

@@ -373,6 +373,9 @@ def get_opc_config():
         "write_counter_node": opc_service.write_counter_node,
         "write_source_node": opc_service.write_source_node,
         "write_target_node": opc_service.write_target_node,
+        "write_s7_endpoint": opc_service.write_s7_endpoint,
+        "write_s7_rack": opc_service.write_s7_rack,
+        "write_s7_slot": opc_service.write_s7_slot,
         "write_nodes": opc_service.write_nodes,
         "running": opc_service.running,
         "last_counter": opc_service.last_counter,
@@ -392,6 +395,9 @@ async def save_opc_config(config: OpcConfig):
     opc_service.write_counter_node = config.write_counter_node
     opc_service.write_source_node = config.write_source_node
     opc_service.write_target_node = config.write_target_node
+    opc_service.write_s7_endpoint = config.write_s7_endpoint
+    opc_service.write_s7_rack = config.write_s7_rack
+    opc_service.write_s7_slot = config.write_s7_slot
     opc_service.write_nodes = config.write_nodes
     opc_service.write_counter_last = None
     try: