High-level architecture

Screens render feature UI, feature UI updates app state, app state persists through repositories into SQLite. Reminder times flow sideways into the device layer, which reconciles them with OS alarms. Nothing leaves the device unless a signed-in account exists — then the outbox carries edits to Firestore and listeners bring other devices' edits back.

Solid lines are on-device data; dashed lines are optional cloud sync, only active for signed-in accounts with Firebase configured.

Sources: README.md, implementation.md, src/app/_layout.tsx (documented at commit 99a2c3d)