feat(apps): add to nixFastBuild and clean up nix code

checks/apps.nix

@@ -0,0 +1,13 @@
+{
+  pkgs,
+  self,
+}: let
+  inherit (pkgs.lib) mapAttrs' nameValuePair removeAttrs removeSuffix;
+in
+  mapAttrs'
+  (name: app:
+    nameValuePair "app-${name}" (pkgs.symlinkJoin {
+      name = "app-${name}";
+      paths = [(removeSuffix "/bin/${name}" (toString app.program))];
+    }))
+  (removeAttrs self.apps.${pkgs.system} ["genflake"])

checks/default.nix

@@ -2,6 +2,7 @@
   pkgs,
   self,
 }: let
+  apps = import ./apps.nix {inherit pkgs self;};
   nixosMachines = import ./machines.nix {inherit pkgs self;};
 in
-  nixosMachines
+  apps // nixosMachines