There isn't a way to see it in game, but it's stored in the save file.
In the BronzeAge directory, under "saves", open the world's save file (these files are big, it might take a bit).
The seed is stored on the second line, something like this:
<world schema="1" name="Itera The Lands Of Hammering" seed="62777761" date="1/13/0543 4:13:09 PM" hostility="0.25">
Yours will look slightly different, this is taken from a save from a previous version of Bronze Age.