dregil: Import current config into flake

modules/common-system.nix

@@ -0,0 +1,49 @@
+{config, pkgs, inputs, ...}:
+{
+  i18n.defaultLocale = "en_US.UTF-8";
+  time.timeZone = "Europe/Berlin";
+
+  environment.systemPackages = with pkgs; [
+    wget
+    tmux
+    ripgrep
+    git
+    dua
+    erdtree
+    exa
+    fd
+    fzf
+    bat
+  ];
+
+  networking.firewall.enable = true;
+
+  users.users.alex = {
+      isNormalUser = true;
+      extraGroups = [ "wheel" "input" ];
+      shell = pkgs.zsh;
+  };
+
+  nix = {
+      gc = {
+        automatic = true;
+        dates = "weekly";
+        options = "--delete-older-than 30d";
+      };
+
+      registry = {
+        nixpkgs.flake = inputs.nixpkgs;
+        nixpkgs-unstable.flake = inputs.nixpkgs-unstable;
+      };
+
+      settings = {
+        auto-optimise-store = true;
+        experimental-features = [ "nix-command" "flakes" ];
+        warn-dirty = false;
+
+        # avoid unwanted garbage collection when using direnv
+        keep-outputs = true;
+        keep-derivations = true;
+      };
+  };
+}