M39: harden application and acceptance gates

frontend/src/context/AuthContext.tsx

@@ -18,8 +18,14 @@ const AuthContext = createContext<AuthState | undefined>(undefined);
 const STORAGE_KEY = "mobilityops.demo-user";
 
 function readCachedUser(): CurrentUser | null {
-  const stored = sessionStorage.getItem(STORAGE_KEY);
-  return stored ? (JSON.parse(stored) as CurrentUser) : null;
+  try {
+    const stored = sessionStorage.getItem(STORAGE_KEY);
+    return stored ? (JSON.parse(stored) as CurrentUser) : null;
+  } catch {
+    // A corrupted or blocked sessionStorage must never prevent the app from booting;
+    // the session endpoint remains the source of truth.
+    return null;
+  }
 }
 
 function cacheUser(user: CurrentUser | null) {