fix: harden IPv4 address string handling

[hlolli]

Replace the IPv4 logging paths in the interface code with bounded inet_ntop conversions instead of copying inet_ntoa output with strncpy. The previous code depended on implicit null termination, which is exactly the kind of edge case static analysis tools flag because it can turn a harmless log line into undefined behavior if the buffer contents are ever reused as a C string.

This keeps the behavior the same for normal traffic, but makes the code explicit about buffer sizing and string termination. It also centralizes the conversion in a tiny helper so future address logging in this file can reuse the safer path instead of open-coding it again.