user/spicetify: link spicetify to .local/bin

when switching themes using home-manager specialisations, the user
environment in /etc/profiles/per-user is not updated (managed by nixos),
so we create a symlink here to force it to use the current hm config's
spicetify (.local/bin has higher priority)

this is a workaround at best, a hack at worst. should probably somehow
make /etc/profiles irrelevant and use something else user-managed.

modules/user/spicetify.nix

@@ -1,4 +1,4 @@
-{ config, inputs, pkgs, ... }:
+{ config, inputs, lib, pkgs, ... }:
 let
   spicePkgs = inputs.spicetify-nix.legacyPackages.${pkgs.system};
 in
@@ -46,4 +46,6 @@ in
       volumePercentage
     ];
   };
+
+  home.file.".local/bin/spotify".source = lib.getExe config.programs.spicetify.spicedSpotify;
 }