Refactor server reducer into TypeScript (#39089)

app/javascript/mastodon/features/ui/components/navigation_bar.tsx

@@ -84,10 +84,7 @@ const NotificationsButton = () => {
 const LoginOrSignUp: React.FC = () => {
   const dispatch = useAppDispatch();
   const signupUrl = useAppSelector(
-    (state) =>
-      (state.server.getIn(['server', 'registrations', 'url'], null) as
-        | string
-        | null) ?? '/auth/sign_up',
+    (state) => state.server.server.item?.registrations.url ?? '/auth/sign_up',
   );
 
   const openClosedRegistrationsModal = useCallback(() => {
@@ -95,7 +92,7 @@ const LoginOrSignUp: React.FC = () => {
   }, [dispatch]);
 
   useEffect(() => {
-    dispatch(fetchServer());
+    void dispatch(fetchServer());
   }, [dispatch]);
 
   if (sso_redirect) {

app/javascript/mastodon/features/ui/components/report_collection_modal.tsx

@@ -52,7 +52,7 @@ export const ReportCollectionModal: React.FC<{
   const account = useAccount(account_id);
 
   useEffect(() => {
-    dispatch(fetchServer());
+    void dispatch(fetchServer());
   }, [dispatch]);
 
   const [submitState, setSubmitState] = useState<