feat: 完成TCP2UART透传核心集成

集成CH390驱动、LwIP协议栈和FreeRTOS多任务透传框架，确保TCP Server/Client与UART链路按配置稳定联动。

Drivers/LwIP/src/include/netif/ethernetif.h

@@ -0,0 +1,27 @@
+#ifndef _ETHERNETIF_H_
+#define _ETHERNETIF_H_
+
+#include "lwip/netif.h"
+
+extern struct netif ch390_netif;
+
+/**
+ * Helper struct to hold private data used to operate your ethernet interface.
+ * Keeping the ethernet address of the MAC in this struct is not necessary
+ * as it is already kept in the struct netif.
+ * But this is only an example, anyway...
+ */
+struct ethernetif {
+//    struct eth_addr *ethaddr;
+    /* Add whatever per-interface state that is needed here. */
+    uint16_t rx_len;
+    uint8_t rx_status;
+};
+
+void init_lwip_netif(const ip4_addr_t *ipaddr, const ip4_addr_t *netmask, const ip4_addr_t *gw);
+err_t ethernetif_init(struct netif *netif);
+void ethernetif_input(struct netif *netif);
+
+void print_netif(struct netif *netif);
+
+#endif /* _ETHERNETIF_H_ */