Update Nix flake, refactor Darwin app aliases and use it for system and

home config. Remove qutebrowser, mousecat, move some apps from brew ->
nixpkgs, add firefox to mac

nix/utils.nix

@@ -1,4 +1,4 @@
-{
+rec {
   mk_symlinks =
     {
       config,
@@ -13,4 +13,37 @@
         };
       }) dotfiles
     );
+
+  mkAppAliasSystem = args: args.pkgs.lib.mkForce (mkAppAliasScriptContent args);
+  mkAppAliasHome =
+    args: args.lib.hm.dag.entryAfter [ "writeBoundary" ] (mkAppAliasScriptContent args);
+
+  # Darwin System / Home Manager expects activation scripts in different formats
+  # This only return the script body, use the other two functions in the config.
+  mkAppAliasScriptContent =
+    {
+      derivationName,
+      appsPath,
+      outputDir,
+      pkgs,
+      lib,
+    }:
+    let
+      env = pkgs.buildEnv {
+        name = derivationName;
+        paths = appsPath;
+        pathsToLink = "/Applications";
+      };
+    in
+    ''
+      echo "Setting up macOS .app aliases..." >&2
+      rm -rf "${outputDir}"
+      mkdir -p "${outputDir}"
+
+      find ${env}/Applications -maxdepth 1 -type l -exec readlink '{}' + |
+      while read -r src; do
+        app_name=$(basename "$src")
+        ${pkgs.mkalias}/bin/mkalias "$src" "${outputDir}/$app_name"
+      done
+    '';
 }