Fix: Add portable tc_htonl/tc_htons/tc_ntohl/tc_ntohs macros, replace winsock2-incompatible hton*/nto* in NAT test files

lib/platform_compat.h

@@ -153,6 +153,12 @@
 
 #include <stdint.h>
 
+// Portable byte-order: no winsock2, no struct in_addr, pure C
+static inline uint16_t tc_htons(uint16_t x) { return (uint16_t)(((x & 0xFFU) << 8) | ((x & 0xFF00U) >> 8)); }
+static inline uint32_t tc_htonl(uint32_t x) { return (((x & 0x000000FFU) << 24) | ((x & 0x0000FF00U) << 8) | ((x & 0x00FF0000U) >> 8) | ((x & 0xFF000000U) >> 24)); }
+#define tc_ntohs(x) tc_htons(x)
+#define tc_ntohl(x) tc_htonl(x)
+
 // Generate cryptographically secure random bytes
 // Returns 0 on success, -1 on error
 int random_bytes(uint8_t *buffer, size_t len);