feat(06-05): global session-expiry interstitial via QueryCache/MutationCache onError

- Add sessionExpired boolean + setSessionExpired action to Zustand calendarStore
- main.tsx: construct QueryClient with QueryCache+MutationCache onError (v5 pattern, not defaultOptions.onError)
- onGlobalError: checks instanceof SessionExpiredError, calls setSessionExpired(true) via store.getState()
- CalendarShell: read sessionExpired from store; render AuthSplash(state=redirecting, 'Session expired', 'Signing you back in…')
- CalendarShell: useEffect fires clearLoginRedirect + maybeRedirectToLogin after 1.5s when sessionExpired (one-shot guard re-armed)
- Context7 /tanstack/query confirmed v5 QueryCache/MutationCache constructor + onError signature

apps/pwa/src/main.tsx

@@ -10,11 +10,32 @@ import './styles/index.css'
 
 import React from 'react'
 import ReactDOM from 'react-dom/client'
-import { QueryClient, QueryClientProvider } from '@tanstack/react-query'
+import { QueryClient, QueryClientProvider, QueryCache, MutationCache } from '@tanstack/react-query'
 import App from './App.js'
 import { ErrorBoundary } from './components/ErrorBoundary.js'
+import { SessionExpiredError } from './api/client.js'
+import { useCalendarStore } from './store/calendarStore.js'
+
+/**
+ * Global session-expiry error handler (D-11, Plan 06-05).
+ *
+ * When any query or mutation throws a SessionExpiredError, arm the interstitial
+ * via the Zustand store's imperative getter — safe to call outside React since
+ * Zustand's create() returns a store with a .getState() API.
+ *
+ * QueryCache and MutationCache onError callbacks are the correct v5 pattern for
+ * global error handling (NOT defaultOptions.onError, which was removed in v5).
+ * Confirmed via Context7 /tanstack/query docs for v5.101.0.
+ */
+function onGlobalError(error: unknown): void {
+  if (error instanceof SessionExpiredError) {
+    useCalendarStore.getState().setSessionExpired(true)
+  }
+}
 
 const queryClient = new QueryClient({
+  queryCache: new QueryCache({ onError: onGlobalError }),
+  mutationCache: new MutationCache({ onError: onGlobalError }),
   defaultOptions: {
     queries: {
       retry: 1,