moongreet/moonlock/moonset link against gtk4 headers at build time.
The CI workflow runs `makepkg -sfd` and only installs makedepends
explicitly — with gtk4 listed only in depends, the build container
had no cairo.pc / gtk4.pc and cairo-sys-rs failed to find the
system library. Add gtk4, gtk4-layer-shell, pkgconf (plus
gtk-session-lock + pam for moonlock) to makedepends.
This previously only worked because repeated `makepkg -s` runs
left the libs installed in the act_runner container filesystem.
Recreating the runner today exposed the latent gap.
Add PKGBUILDs for moonset-git, moonlock-git, and moongreet-git.
Intended as a paru custom AUR source for easy installation of
all Moonarch components via `paru -S moonset-git`.
