I need a fully-featured calendar application that runs smoothly on both iOS and Android. The core of the project is straightforward: let users create events, get timely reminders, manage to-dos in the same space, and keep everything in sync with their existing Google, Outlook, or Apple calendars. On the technical side, I’m open to your preferred stack—whether that’s Flutter, React Native, Swift/Kotlin with a shared backend, or something else—so long as the final builds feel consistent across devices and pass App Store and Google Play review. Key deliverables • Native-feeling iOS and Android apps, each store-ready • Reliable event reminder system (push notifications, local alerts) • Integrated task manager that links tasks to specific dates or events • Two-way synchronization with major calendar providers (CalDAV/Google API, Microsoft Graph, etc.) • Clean, intuitive UI—simple for now, but structured so additional appearance options can be added later Please outline your proposed architecture, estimated timeline, and any similar apps you’ve shipped. A short test build or repo snapshot demonstrating calendar sync will help me evaluate quickly.