nixos: create 'modules/nixos' folder

Let's consolidate all modules under one path, so that NixOS,
home-manager, and nix-darwin (if I ever end up using it down the line)
would go under the same folder.

modules/nixos/services/default.nix

@@ -0,0 +1,40 @@
+{ ... }:
+
+{
+  imports = [
+    ./adblock
+    ./backup
+    ./blog
+    ./calibre-web
+    ./drone
+    ./fail2ban
+    ./flood
+    ./gitea
+    ./grocy
+    ./indexers
+    ./jellyfin
+    ./lohr
+    ./matrix
+    ./miniflux
+    ./monitoring
+    ./navidrome
+    ./nextcloud
+    ./nginx
+    ./nix-cache
+    ./paperless
+    ./pirate
+    ./podgrab
+    ./postgresql
+    ./postgresql-backup
+    ./quassel
+    ./rss-bridge
+    ./sabnzbd
+    ./ssh-server
+    ./tandoor-recipes
+    ./tlp
+    ./transmission
+    ./vikunja
+    ./wireguard
+    ./woodpecker
+  ];
+}