feat(home-manager): add core+extras profile and wire it into vps

Introduce myHomeProfile.extraPrograms (mirrors myPackages.extra) so each
host's NixOS config declares which extra Home Manager modules it needs
on top of a shared core (fish, starship, btop, git). miku-homelab's
former home.nix becomes its extras list; vps gets home-manager for the
first time using core alone.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

hosts/vps/default.nix

@@ -1,9 +1,10 @@
-{ config, ... }:
+{ config, pkgs, ... }:
 
 {
   imports = [
     ./hardware-configuration.nix
     ../../modules/profiles/server.nix
+    ../../modules/system/home-profile.nix
     ../../modules/system/packages.nix
   ];
 
@@ -39,6 +40,7 @@
   myUsers = {
     admins.emmatherock = {
       description = "EmmaTheRock";
+      shell = pkgs.fish;
       extraGroups = [ "wheel" ];
       authorizedKeys = [
         "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIA8vfwM5g9RJXqHtqTgNqsYg9SxSm+UMvFqTjBoAsLJ6 emmatherock@MAIN-PC"