refactor: move qrCodeStore to lib/stores for better organization

The qrCodeStore has been relocated from the app/stores directory to app/lib/stores to maintain a more consistent and organized project structure. This change improves maintainability by centralizing store-related files in a dedicated directory.

app/lib/stores/qrCodeStore.ts

@@ -0,0 +1,3 @@
+import { atom } from 'nanostores';
+
+export const expoUrlAtom = atom<string | null>(null);