CVE-2026-79981: The DNS stub resolver in subsys/net/lib/dns/resolve.c binds one UDP socket per configured server when the resolver context is initialised (dns_resolve_init_lock

The DNS stub resolver in subsys/net/lib/dns/resolve.c binds one UDP socket per configured server when the resolver context is initialised (dns_resolve_init_locked() -> register_dispatcher() -> dns_dispatcher_register()), with the local port left at 0 so the stack picks an ephemeral port exactly once. dns_write() then sends every subsequent query from that same socket without re-binding, so the source port is constant for the lifetime of the resolver context while only the 16-bit transaction iden