feat(260606-tv8-01): wire login redirect into CalendarShell meQuery handling

- Import maybeRedirectToLogin + clearLoginRedirect from loginRedirect.ts
- useEffect on meQuery.isError calls maybeRedirectToLogin() (one-shot, loop-guarded)
- useEffect on meQuery.isSuccess calls clearLoginRedirect() for future re-auth
- Existing 'Sign-in required' branch retained as fall-through for already-attempted case

apps/pwa/src/components/CalendarShell.tsx

@@ -43,6 +43,7 @@ import { Plus } from 'lucide-react'
 
 import { fetchMe, fetchEvents } from '../api/client.js'
 import { hydrateEvents } from '../lib/hydrateEvents.js'
+import { maybeRedirectToLogin, clearLoginRedirect } from '../lib/loginRedirect.js'
 import { buildCalendarConfig, SX_FIRST_DAY_OF_WEEK } from '../lib/calendarConfig.js'
 import { useCalendarStore } from '../store/calendarStore.js'
 import { EventDetailPopover } from './EventDetailPopover.js'
@@ -174,6 +175,26 @@ export function CalendarShell() {
     eventsService.set(sxEvents as Parameters<typeof eventsService.set>[0])
   }, [eventsQuery.data, eventsService])
 
+  // Auth redirect — one-shot full-page nav to /api/login when /api/me fails.
+  // If this is the first failure, maybeRedirectToLogin() sets a sessionStorage
+  // flag and navigates the browser to /api/login (top-level nav, no CORS block).
+  // The page will unmount as the browser navigates. If the flag is already set
+  // (already bounced through login once and still failing), returns false and the
+  // existing "Sign-in required" branch below renders.
+  useEffect(() => {
+    if (meQuery.isError) {
+      maybeRedirectToLogin()
+    }
+  }, [meQuery.isError])
+
+  // Clear the one-shot flag on a successful /api/me load so a later session
+  // expiry can trigger another redirect instead of showing "Sign-in required".
+  useEffect(() => {
+    if (meQuery.isSuccess) {
+      clearLoginRedirect()
+    }
+  }, [meQuery.isSuccess])
+
   // ── Render helpers ────────────────────────────────────────────────────────
 
   // Determine which content to show in the calendar area