Add IP version badge to Link Pool form dropdowns

<img width="998" height="797" alt="Image" src="https://github.com/user-attachments/assets/4d03cc4d-a189-486f-a953-a31cbc714567" />
One of these is a `v4`! One is a `v6`! But which is which? A badge in the dropdown would help. Possibly also a `UNICAST` / `MULTICAST` badge while we're at it.