Fix: align local build binary names

[mayc7n]

This PR updates the local build targets to match the documented and released binaries.

Changes

• Changed the default make build output from abacate to abacatepay
• Added ALIAS_BINARY=abkt
• Added a build-aliases target to build both abacatepay and abkt

Validation

I validated the generated commands with:

make -n build
make -n build-aliases

Output:

go build -o abacatepay .
go build -o abacatepay .
go build -o abkt .

I couldn't run the full Go test suite locally because Go is not installed in my current environment.