feat(16-04): show internalName with AD-name fallback in groups list

Name column renders group.internalName ?? group.name (nullish, not
truthiness, since the backend already normalizes blank values to null)
inside a span carrying title={group.name} so the AD name stays
discoverable on hover once an internal name is set. Badge column is
untouched — it remains the sole imported-vs-local marker per D-07.

Adds two component-test cases covering the fallback and its title
attribute (D-04).

apps/web/src/app/(portal)/admin/groups/page.tsx

@@ -177,7 +177,9 @@ export default function AdminGroupsPage() {
             <tbody className="divide-y divide-border">
               {groups.map((group) => (
                 <tr key={group.id} className="hover:bg-muted/30 transition-colors">
-                  <td className="px-4 py-3 font-medium text-foreground">{group.name}</td>
+                  <td className="px-4 py-3 font-medium text-foreground">
+                    <span title={group.name}>{group.internalName ?? group.name}</span>
+                  </td>
                   <td className="px-4 py-3">
                     <span
                       className={`inline-block rounded-full px-2 py-0.5 text-xs font-medium ${