feat(sync): add cloud synchronization for favorites

Add a new sync service and frontend integration to allow syncing
favorites across devices using a token.

- Configure `sync-service` in docker-compose.yml on port 7482
- Add sync token input and manual sync button to SideDrawer
- Implement auto-sync logic to persist favorites to the KV store
- Add logic to merge cloud favorites with local data on initialization

sync-server/Dockerfile

@@ -0,0 +1,9 @@
+FROM node:18-alpine
+
+WORKDIR /app
+
+COPY server.js .
+
+EXPOSE 3001
+
+CMD ["node", "server.js"]