Move CLI crate to root of workspace

Somehow I missed that this was a thing you could do? It's a much
cleaner organization, and it makes it so that you don't have to
explicitly specify the crate to build.

flake.nix

@@ -30,7 +30,6 @@
             pname = "ggelo";
             version = "0.1.0";
             src = craneLib.path ./.;
-            cargoBuildFlags = "-p cli";
             buildInputs = [ pkgs.openssl pkgs.sqlite ];
             nativeBuildInputs = [ pkgs.pkg-config ];
           };