chore: remove features.old archive and format all files

- Delete home/features.old/ (archived old flat feature modules)
- All content migrated to new profile-based structure
- Run alejandra formatter over 13 changed files
- nix flake check passes cleanly

hosts/m3-ares/services/postgres.nix

@@ -1,7 +1,4 @@
-{
-  pkgs,
-  ...
-}: {
+{pkgs, ...}: {
   services.postgresql = {
     enable = true;
     package = pkgs.postgresql_17;