-- Tracks how far back a full backfill has already reached. Garmin activity
-- history is immutable once recorded, so once we've backfilled a historical
-- window there is no need to ever re-fetch get_activities() for it again --
-- this is the "cache" that lets repeated backfills be cheap/fast instead of
-- re-walking years of history against Garmin's API every time.
CREATE TABLE sync_state (
    id                   INTEGER PRIMARY KEY CHECK (id = 1),
    earliest_synced_date TEXT,
    backfill_complete    INTEGER NOT NULL DEFAULT 0
);
INSERT INTO sync_state (id, earliest_synced_date, backfill_complete) VALUES (1, NULL, 0);