- Add lib/getmyip.c/h with get_outgoing_local_ip() using UDP connect+getsockname
- Update etcp_socket_add() to use new function for 0.0.0.0 and :: bindings
- Support both IPv4 (8.8.8.8) and IPv6 (2001:4860:4860::8888) auto-detection
- Remove broken get_default_route_ip() from platform_compat (it returned gateway IP, not local IP)
- Keep get_interface_ip_by_index() for explicit interface bindings
- Update Makefile.am to include new getmyip module
- New lib/getmyip.c/h with get_outgoing_ip(), get_default_local_ip(), get_local_ip_by_index()
- Uses UDP connect + getsockname instead of /proc/net/route parsing
- Supports both IPv4 and IPv6
- Updated etcp_socket_add() to use new functions for interface_addr detection