refactor: move last legacy_modules to modules

modules/programs/spotify.nix

@@ -0,0 +1,27 @@
+# Enabled when: desktop
+{
+  config,
+  lib,
+  username,
+  pkgs,
+  ...
+}: {
+  config = lib.mkIf config.fireproof.desktop.enable {
+    environment.systemPackages = with pkgs; [
+      spotify
+    ];
+
+    age.secrets.spotify-player = {
+      rekeyFile = ../../secrets/spotify-player.age;
+      path = "/home/${username}/.cache/spotify-player/credentials.json";
+      mode = "0600";
+      owner = username;
+    };
+
+    fireproof.home-manager = {
+      programs.spotify-player = {
+        enable = true;
+      };
+    };
+  };
+}