Fix IPv6 random IP logic error

[ImAubrey]

Optimize the random IP algorithm logic and fix the problem of random IP errors when the prefix is not divisible by 8.

[Fangliding]

Very grateful
I did think of the situation of the prefix might not divisible by 8 and put it on the schedule, but I forgot it in the end😂

[ImAubrey]

Very grateful I did think of the situation of the prefix might not divisible by 8 and put it on the schedule, but I forgot it in the end😂

I came across the update in version 1.8.10 by chance and started using it. Yesterday, I had my own IPv6 Prefix, but my announce was /47. At first, when I filled in /47, I thought it was a problem with my network. It was only after examining the code that I realized this minor issue.

Additionally, in my opinion, converting the IP address and prefix directly into a range, then randomly generating a number within this range, and finally converting this number back to an IP address might be more efficient.

Ha, no worries at all! Glad I could help!

[yuhan6665]

looks great!