fix(webapp): read impersonation state from useIsImpersonating in GlobalShortcuts

useOptionalUser returns UserWithDashboardPreferences, which has no
isImpersonating field (it comes from the org loader), so referencing
user.isImpersonating failed the typecheck. Source it from useIsImpersonating,
the same hook useHasAdminAccess uses.

Author: samejr

apps/webapp/app/components/GlobalShortcuts.tsx

@@ -1,15 +1,16 @@
 import { useNavigate, useSubmit } from "@remix-run/react";
 import { useEffect } from "react";
+import { useIsImpersonating } from "~/hooks/useOrganizations";
 import { useOptionalUser } from "~/hooks/useUser";
 import { adminPath } from "~/utils/pathBuilder";
 
 /** App-wide keyboard shortcuts, mounted once at the root so they work everywhere. Renders nothing. */
 export function GlobalShortcuts() {
   const user = useOptionalUser();
+  const isImpersonating = useIsImpersonating();
   const navigate = useNavigate();
   const submit = useSubmit();
 
-  const isImpersonating = Boolean(user?.isImpersonating);
   const isAdmin = Boolean(user?.admin) || isImpersonating;
 
   useEffect(() => {