fix(auth): preserve session on reload and correct 401 redirect flow

- Save PKCE params to sessionStorage.redirectState on 401 instead of overwriting tokenSet

- Persist userData in sessionStorage after OIDC callback for later hydration

- Hydrate Redux (tokens + userData) from sessionStorage on app start to avoid forced re-login

- Keep SPA single route '/' behavior unchanged; only improves auth robustness

Files: src/utils/apiUtils.ts, src/features/User/LoginCallback.tsx, src/features/User/HandleLogin.tsx

src/features/User/HandleLogin.tsx

@@ -5,6 +5,7 @@ import { Loading } from "../../components/Loading/Loading";
 import { Error } from "../../components/Error/Error";
 import { push } from "redux-first-history";
 import { redirectTo } from "../../utils/apiUtils";
+import { setTokens, setUserData } from "./userSlice";
 
 export function HandleLogin() {
   const userData = useAppSelector((state) => state.user);
@@ -13,6 +14,20 @@ export function HandleLogin() {
   useEffect(() => {
     const initiateLogin = async () => {
       if (!userData.userData) {
+        const savedToken = sessionStorage.getItem("tokenSet")
+          ? JSON.parse(sessionStorage.getItem("tokenSet")!)
+          : null;
+        const savedUser = sessionStorage.getItem("userData")
+          ? JSON.parse(sessionStorage.getItem("userData")!)
+          : null;
+
+        if (savedToken && savedUser) {
+          dispatch(setTokens(savedToken));
+          dispatch(setUserData(savedUser));
+          dispatch(push("/"));
+          return;
+        }
+
         const loginurl = await Auth();
 
         sessionStorage.setItem(
@@ -28,7 +43,7 @@ export function HandleLogin() {
     };
 
     initiateLogin();
-  }, [userData]);
+  }, [userData, dispatch]);
 
   if (!calendars.pending && !userData.loading) {
     dispatch(push("/error"));

src/features/User/LoginCallback.tsx

@@ -27,6 +27,7 @@ export function CallbackResume() {
 
         sessionStorage.removeItem("redirectState");
         sessionStorage.setItem("tokenSet", JSON.stringify(data?.tokenSet));
+        sessionStorage.setItem("userData", JSON.stringify(data?.userinfo));
         // Redirect to main page after successful callback
         dispatch(push("/"));
       } catch (e) {

src/utils/apiUtils.ts

@@ -23,7 +23,7 @@ export const api = ky.extend({
           const loginurl = await Auth();
 
           sessionStorage.setItem(
-            "tokenSet",
+            "redirectState",
             JSON.stringify({
               code_verifier: loginurl.code_verifier,
               state: loginurl.state,