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>

home/emmatherock/core.nix

@@ -0,0 +1,11 @@
+{
+  imports = [
+    ./git.nix
+    ./shell.nix
+  ];
+
+  programs.home-manager.enable = true;
+  programs.btop.enable = true;
+
+  home.stateVersion = "25.11";
+}

home/emmatherock/home.nix

@@ -1,18 +0,0 @@
-{
-  imports = [
-    ./agents.nix
-    ./audio.nix
-    ./desktop-apps.nix
-    ./deskflow.nix
-    ./gaming.nix
-    ./git.nix
-    ./media.nix
-    ./packages.nix
-    ./plasma.nix
-    ./shell.nix
-    ./vscode.nix
-  ];
-
-  programs.home-manager.enable = true;
-  home.stateVersion = "25.11";
-}

home/emmatherock/packages.nix

@@ -1,10 +1,11 @@
 { pkgs, ... }:
 {
+  programs.btop.package = pkgs.btop.override { cudaSupport = false; rocmSupport = true; };
+
   home.packages = with pkgs; [
     # --- Base y Terminal ---
     vim
     fastfetch
-    (btop.override { cudaSupport = false; rocmSupport = true; })
     nvtopPackages.full
   ];
 }