feat: migrate command scripts to just

- Replaced bin/ shell scripts with a Justfile
- Added deploy commands and 2 new commands (update, gc)
- Added just to devShell

flake.nix

@@ -89,11 +89,8 @@
               pkgs.sops
               pkgs.git
               pkgs.git-crypt
+              pkgs.just
             ];
-
-            shellHook = ''
-              export PATH=${builtins.toPath ./bin}:$PATH
-            '';
           };
         }
       );