You are a senior mobile app developer experienced in building health and fitness applications. I want to develop a fitness tracking mobile app using [your preferred mobile development framework or language]. Please provide a detailed development plan that includes:

• Core architecture and recommended folder structure
• Integration with device sensors (e.g., GPS, pedometer, heart rate monitor)
• User authentication and secure data storage for workout history and personal metrics
• Real-time activity tracking and visualization (e.g., maps, progress charts, streaks)
• Offline functionality and data sync with cloud storage when connected
• Health data integration (e.g., Apple HealthKit, Google Fit)
• Push notifications for goals, reminders, and milestone achievements
• CI/CD setup for continuous testing, deployment, and release to app stores

Ensure your plan includes best practices for performance optimization, user privacy, and compliance with health data regulations. Recommend libraries, tools, and design patterns to streamline development.