chore!: use gosh for building assets

This is a breaking change because it makes Anubis rely on Go 1.25
ahead of #1525. I think that the change is worth it, but Fedora
et.al updates slowly and I really don't want to rock the boat.

One of the main reasons to do this is that this enables the ability
to build Anubis on Windows (#1304).

Signed-off-by: Xe Iaso <me@xeiaso.net>

web/embed.go

@@ -3,6 +3,7 @@ package web
 import "embed"
 
 //go:generate go tool github.com/a-h/templ/cmd/templ generate
+//go:generate go tool gosh ./build.sh
 
 var (
 	//go:embed static