Write in {{tone}} tone. Design a {{app_type}} mobile app for the {{industry}} industry with {{visual_style}} design style using Flutter + Riverpod. Output a playbook with Overview, Prerequisites, Step-by-step Plays (Core Features, User Flows, Architecture, Data Layer, Component Architecture, Platform-Specific, Performance, Testing, App Store), Metrics to Track, and Troubleshooting Guide. Maximum 1800 words. Use plain language for intermediate Flutter developers. Skip any section if information is unknown.