feat: add About Me dialog showing user info, roles, and groups

- Add GET /api/v1/auth/me endpoint returning current user's UserDetail
- Add AboutMeDialog component with role badges and group memberships
- Add userMenuItems prop to TopBar via design-system update
- Wire "About Me" menu item into user dropdown above Logout

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/src/api/queries/auth.ts

@@ -0,0 +1,48 @@
+import { useQuery } from '@tanstack/react-query';
+import { config } from '../../config';
+import { useAuthStore } from '../../auth/auth-store';
+
+export interface RoleSummary {
+  id: string;
+  name: string;
+  system: boolean;
+  source: string;
+}
+
+export interface GroupSummary {
+  id: string;
+  name: string;
+}
+
+export interface UserDetail {
+  userId: string;
+  provider: string;
+  email: string;
+  displayName: string;
+  createdAt: string;
+  directRoles: RoleSummary[];
+  directGroups: GroupSummary[];
+  effectiveRoles: RoleSummary[];
+  effectiveGroups: GroupSummary[];
+}
+
+async function fetchMe(): Promise<UserDetail> {
+  const token = useAuthStore.getState().accessToken;
+  const res = await fetch(`${config.apiBaseUrl}/auth/me`, {
+    headers: {
+      ...(token ? { Authorization: `Bearer ${token}` } : {}),
+      'X-Cameleer-Protocol-Version': '1',
+    },
+  });
+  if (!res.ok) throw new Error(`API error: ${res.status}`);
+  return res.json();
+}
+
+export function useMe(enabled = false) {
+  return useQuery({
+    queryKey: ['auth', 'me'],
+    queryFn: fetchMe,
+    enabled,
+    staleTime: 30_000,
+  });
+}