Move app to apps/web-react in pnpm workspace layout

apps/web-react/app/features/timezone/timezone-context.server.ts

@@ -0,0 +1,16 @@
+import { AsyncLocalStorage } from "node:async_hooks";
+
+interface ViewerTimezoneContext {
+	timezone: string | null;
+}
+
+export const viewerTimezoneAsyncLocalStorage =
+	new AsyncLocalStorage<ViewerTimezoneContext>();
+
+/**
+ * The viewer's IANA timezone for the current request. `null` when the browser has
+ * not reported it yet, which is the case for a device's very first document request.
+ */
+export function getViewerTimezone(): string | null {
+	return viewerTimezoneAsyncLocalStorage.getStore()?.timezone ?? null;
+}