Ukrainian Calendar — Cross-Platform Mobile App

Create a mobile companion to the MCP Ukrainian Calendar — a consumer-facing app that delivers the same authentic cultural content (holidays, deities, traditions based on Voytovych's research) directly to users' phones. Key requirements: push notifications before each holiday, calendar integration, offline access, and bilingual UI.

Built a full-stack mobile solution: React Native 0.81 with Expo 54 for cross-platform deployment (iOS + Android from single codebase). Express.js backend with PostgreSQL stores all event data, images, and user preferences. Firebase Cloud Messaging handles daily push notifications via node-cron scheduled jobs.

Features: calendar view with holiday highlighting, detailed event pages (descriptions, traditions, preparation guides, images), Google Calendar integration for one-tap event adding, configurable notification preferences, and offline caching via AsyncStorage. Security: Helmet.js, rate limiting (100 req/15min), CORS, input validation.

Published on the App Store. The app serves as a digital preservation tool for Ukrainian pre-Christian cultural heritage, making ethnographic knowledge from Voytovych's research accessible to a mobile audience. Push notifications ensure users never miss important traditional celebrations.