Add Zsh shell to Darwin services and setup Harald's dev environment

Add Zsh to the list of available shells in the Darwin services module.
Introduce new Nix configurations for aarch64-darwin, including system packages and font settings.
Set up user-specific environment for Harald on aarch64-darwin system.

modules/darwin/system/fonts/default.nix

@@ -27,11 +27,14 @@ in
       packages =
         with pkgs;
         [
-          noto-fonts
-          noto-fonts-cjk-sans
-          noto-fonts-cjk-serif
-          noto-fonts-emoji
-          (nerdfonts.override { fonts = [ "Hack" ]; })
+          (nerdfonts.override {
+            fonts = [
+              "Hack"
+              "FiraCode"
+              "DroidSansMono"
+              "JetBrainsMono"
+            ];
+          })
         ]
         ++ cfg.fonts;
     };