Fix mobile white screen when localStorage throws on access (#54) (#55)

## Summary

- Closes #54
- Add `getLocalStorageSafe()` helper in `tokenStorage.js` to handle browsers that expose `localStorage` but throw `SecurityError` on access
- Wrap all JWT token get/set/remove calls in try/catch so auth bootstrap no longer crashes React on mobile

## Problem

On mobile browsers, hesychia.ai flashes the UI briefly after login then goes white. Auth startup reads tokens from `localStorage` without guarding against storage access errors (common in private mode or blocked storage).

## Test plan

- [ ] Open hesychia.ai on mobile Safari/Chrome (normal mode) and sign in — dashboard should render
- [ ] Repeat in private/incognito mode — app should not white-screen (may require re-login each session if storage blocked)
- [ ] Verify existing web login/logout still works on desktop
- [ ] Run `npm test -- tokenStorage` in `llm-fe`Reviewed-on: #55

llm-fe/src/llm-fe/auth/tokenStorage.js

@@ -9,6 +9,21 @@
 export const ACCESS_TOKEN_KEY = "access_token";
 export const REFRESH_TOKEN_KEY = "refresh_token";
 
+/**
+ * Browsers can expose localStorage but throw on access (privacy mode / blocked storage).
+ * @returns {Storage|null}
+ */
+function getLocalStorageSafe() {
+  try {
+    if (typeof window === "undefined" || !window.localStorage) {
+      return null;
+    }
+    return window.localStorage;
+  } catch {
+    return null;
+  }
+}
+
 /**
  * @returns {{ get?: Function, set?: Function, remove?: Function } | undefined}
  */
@@ -24,10 +39,15 @@ function getPreferencesPlugin() {
  * @returns {string|null}
  */
 export function getToken(key) {
-  if (typeof localStorage === "undefined") {
+  const storage = getLocalStorageSafe();
+  if (!storage) {
+    return null;
+  }
+  try {
+    return storage.getItem(key);
+  } catch {
     return null;
   }
-  return localStorage.getItem(key);
 }
 
 /**
@@ -51,10 +71,15 @@ export function getRefreshToken() {
  * @returns {Promise<void>}
  */
 export async function setTokens(access, refresh) {
-  if (typeof localStorage !== "undefined") {
-    localStorage.setItem(ACCESS_TOKEN_KEY, access);
+  const storage = getLocalStorageSafe();
+  if (storage) {
+    try {
+      storage.setItem(ACCESS_TOKEN_KEY, access);
       if (refresh != null) {
-      localStorage.setItem(REFRESH_TOKEN_KEY, refresh);
+        storage.setItem(REFRESH_TOKEN_KEY, refresh);
+      }
+    } catch {
+      /* localStorage unavailable */
     }
   }
 
@@ -75,9 +100,14 @@ export async function setTokens(access, refresh) {
  * @returns {Promise<void>}
  */
 export async function clearTokens() {
-  if (typeof localStorage !== "undefined") {
-    localStorage.removeItem(ACCESS_TOKEN_KEY);
-    localStorage.removeItem(REFRESH_TOKEN_KEY);
+  const storage = getLocalStorageSafe();
+  if (storage) {
+    try {
+      storage.removeItem(ACCESS_TOKEN_KEY);
+      storage.removeItem(REFRESH_TOKEN_KEY);
+    } catch {
+      /* localStorage unavailable */
+    }
   }
 
   const Preferences = getPreferencesPlugin();
@@ -110,7 +140,8 @@ export async function hydrateTokensFromNativeStorage() {
     try {
       const result = await Preferences.get({ key: ACCESS_TOKEN_KEY });
       if (result?.value) {
-        localStorage.setItem(ACCESS_TOKEN_KEY, result.value);
+        const storage = getLocalStorageSafe();
+        storage?.setItem(ACCESS_TOKEN_KEY, result.value);
         access = result.value;
       }
     } catch {
@@ -122,7 +153,8 @@ export async function hydrateTokensFromNativeStorage() {
     try {
       const result = await Preferences.get({ key: REFRESH_TOKEN_KEY });
       if (result?.value) {
-        localStorage.setItem(REFRESH_TOKEN_KEY, result.value);
+        const storage = getLocalStorageSafe();
+        storage?.setItem(REFRESH_TOKEN_KEY, result.value);
         refresh = result.value;
       }
     } catch {