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/groups-page.test.tsx

@@ -96,6 +96,7 @@ interface Group {
   tenantId: string;
   name: string;
   ldapDn: string | null;
+  internalName: string | null;
   isDefault: boolean;
   createdAt: string;
   updatedAt: string;
@@ -108,6 +109,7 @@ const mockGroups: Group[] = [
     tenantId: 't1',
     name: 'Alle Benutzer',
     ldapDn: null,
+    internalName: null,
     isDefault: true,
     createdAt: '2026-01-01T00:00:00.000Z',
     updatedAt: '2026-01-01T00:00:00.000Z',
@@ -118,6 +120,32 @@ const mockGroups: Group[] = [
     tenantId: 't1',
     name: 'Buchhaltung',
     ldapDn: 'CN=Buchhaltung,OU=Gruppen,DC=ctl,DC=local',
+    internalName: null,
+    isDefault: false,
+    createdAt: '2026-01-01T00:00:00.000Z',
+    updatedAt: '2026-01-01T00:00:00.000Z',
+    memberCount: 1,
+  },
+];
+
+const mockGroupsWithInternalName: Group[] = [
+  {
+    id: 'g3',
+    tenantId: 't1',
+    name: 'AD-Vertrieb',
+    ldapDn: 'CN=AD-Vertrieb,OU=Gruppen,DC=ctl,DC=local',
+    internalName: 'Vertrieb',
+    isDefault: false,
+    createdAt: '2026-01-01T00:00:00.000Z',
+    updatedAt: '2026-01-01T00:00:00.000Z',
+    memberCount: 2,
+  },
+  {
+    id: 'g4',
+    tenantId: 't1',
+    name: 'AD-Support',
+    ldapDn: 'CN=AD-Support,OU=Gruppen,DC=ctl,DC=local',
+    internalName: null,
     isDefault: false,
     createdAt: '2026-01-01T00:00:00.000Z',
     updatedAt: '2026-01-01T00:00:00.000Z',
@@ -178,6 +206,35 @@ describe('AdminGroupsPage', () => {
     expect(screen.getByText('1')).toBeInTheDocument();
   });
 
+  it('shows the internal name in the name column and the AD name as title when internalName is set (D-04)', async () => {
+    vi.stubGlobal(
+      'fetch',
+      vi.fn(() => Promise.resolve({ ok: true, json: () => Promise.resolve(mockGroupsWithInternalName) })),
+    );
+
+    render(<AdminGroupsPage />);
+
+    await waitFor(() => {
+      expect(screen.getByText('Vertrieb')).toBeInTheDocument();
+    });
+    expect(screen.queryByText('AD-Vertrieb')).not.toBeInTheDocument();
+    expect(screen.getByText('Vertrieb').closest('span')).toHaveAttribute('title', 'AD-Vertrieb');
+  });
+
+  it('falls back to the stored name in the name column when internalName is not set (D-04)', async () => {
+    vi.stubGlobal(
+      'fetch',
+      vi.fn(() => Promise.resolve({ ok: true, json: () => Promise.resolve(mockGroupsWithInternalName) })),
+    );
+
+    render(<AdminGroupsPage />);
+
+    await waitFor(() => {
+      expect(screen.getByText('AD-Support')).toBeInTheDocument();
+    });
+    expect(screen.getByText('AD-Support').closest('span')).toHaveAttribute('title', 'AD-Support');
+  });
+
   it('toggles the default-group star optimistically and persists via PATCH', async () => {
     const fetchMock = vi.fn((url: string, init?: RequestInit) => {
       if (typeof url === 'string' && url.endsWith('/groups') && (!init || init.method === undefined)) {

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 ${