Habit and goal tracking mobile app

We are launching a mobile app that helps people build habits and reach personal goals, and we are looking for a developer to bring it to life on both iOS and Android. The heart of the product is the daily loop: a person opens the app, marks the habits they kept today, and immediately sees their progress. That moment has to feel light and rewarding, because the whole point is to make coming back tomorrow effortless rather than a chore.

Around that loop we need the features that keep motivation alive. Streaks should count consecutive days and celebrate milestones without shaming a missed day. Reminders must be flexible, so a user can be nudged at the times that actually fit their routine, and they should be easy to snooze or turn off. Statistics should tell an honest, encouraging story over weeks and months, with simple charts a non-technical person can read at a glance. We also want small motivational touches, such as friendly messages and visible goal progress, that reinforce the effort without feeling pushy.

We care about a calm, modern interface and smooth performance on mid-range phones. Data should be stored on the device and, ideally, sync across a user's own devices later. Please share how you would structure the app, which cross-platform or native approach you recommend, how you would handle local notifications reliably, and your view on offline-first storage.