feat: sign zinniad binary for macOS

[bajtos]

This is a follow-up for #158 fixing an accidental omission.

See also #75

[bajtos]

Verified the signature of zinnia & zinniad binaries produced by https://github.com/filecoin-station/zinnia/actions/runs/4553582743.

❯ codesign -d -vv zinniad
Executable=/Users/bajtos/Downloads/archives-macos-arm64/zinniad
Identifier=io.filstation.zinnia
Format=Mach-O thin (arm64)
CodeDirectory v=20400 size=456664 flags=0x0(none) hashes=14265+2 location=embedded
Signature size=8939
Authority=Developer ID Application: Protocol Labs, Inc. (7Y229E2YRL)
Authority=Developer ID Certification Authority
Authority=Apple Root CA
Timestamp=29 Mar 2023 at 13:49:28
Info.plist=not bound
TeamIdentifier=7Y229E2YRL
Sealed Resources=none
Internal requirements count=1 size=180