zen: overhaul configuration

Declaratively configure plugin installation and configuration.

Use my own self-hosted sync server.

home-manager/gui.nix

@@ -2,6 +2,7 @@
   pkgs,
   lib,
   inputs,
+  config,
   ...
 }:
 {
@@ -12,6 +13,7 @@
     ./progs/emacs.nix
     # ./progs/trezor.nix # - broken
     ./progs/flatpak.nix
+    ./progs/zen
   ];
 
   nixpkgs.config.allowUnfreePredicate =
@@ -34,7 +36,6 @@
       # browsers
       [
         tor-browser
-        inputs.zen-browser.packages."${system}".twilight
         grayjay
       ]
 
@@ -171,7 +172,6 @@
   };
 
   home.sessionVariables = {
-    BROWSER = "zen";
     LD_LIBRARY_PATH = "${pkgs.lib.makeLibraryPath [
       pkgs.stdenv.cc.cc
     ]}";