I need a clean, efficient Android-only app that helps users design and follow their own fitness routines. The core experience revolves around two key capabilities: • Workout tracker – log exercises, sets, reps and rest, then surface progress stats in a simple dashboard. • Custom program builder – drag-and-drop or template-based creation of multi-week plans, with the ability to edit on the fly. A lightweight account system is required: email or Google sign-in, basic profile storage, and cloud sync for routines and history—nothing more elaborate such as leaderboards or community messaging at this stage. Material-style UI, smooth navigation and offline functionality are important. Please structure the code clearly (Kotlin or Java), document major classes, and supply the final APK along with source in a Git repo so I can continue iterating after launch. If you foresee optional add-ons like nutritional guidance, note how they could be integrated later without major rework.