odhcpd: update to 25.12 Git HEAD (2025-12-18)

odhcpd: update to 25.12 Git HEAD (2025-12-18)

0779ee287db5 dhcpv6-ia: reconfigure message length bug fix
d69896b0ac7c all: remove dead code
3f6b3b4b9f8a odhcpd: remove fallback DNS search domain
ff3f72fdd01d router: remove some log spam in send_router_advert()
c1cc541e1065 router: improve send_router_advert()
901851b883da router: Modify relayed RA PIO P flag according to interface policy
179429ba477d router: Modify relayed RA PIO A flags according to interface policy

https://github.com/openwrt/odhcpd/compare/cb1b8770b782...0779ee287db5

Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>