Pull request 2525: 4923-gopacket-dhcp-vol.13

Squashed commit of the following:

commit 79d96a231649cecbb41b90796ddf0ae6c6bdba4c
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Tue Nov 18 14:05:37 2025 +0300

    dhcpsvc: imp code, docs

commit 8944c8c44c5306760dda12085af05f37f7bca20f
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Mon Nov 17 17:21:41 2025 +0300

    dhcpsvc: add lease allocation