add aspects/users/ configurations

User-specific home-manager configurations for:
- user@rotterdam
- user@io

Includes user-specific modules in _user/ directory.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

aspects/users/_user/git.nix

@@ -0,0 +1,17 @@
+{ pkgs, ... }:
+
+{
+  programs = {
+    git = {
+      enable = true;
+      settings.user = {
+        name = "William";
+        email = "baduhai@proton.me";
+      };
+    };
+    diff-so-fancy = {
+      enable = true;
+      enableGitIntegration = true;
+    };
+  };
+}