/// The single switch that turns real AdMob ads on.
///
/// While this is `false`, the app behaves in every observable way as though
/// ads were live — each placement is still *decided* on exactly the same
/// schedule (new-user grace periods, earned credits, the ad-free purchase,
/// the sync gate blocking uploads) — but where a real ad would appear, it
/// shows `AdPlaceholderScreen` instead, and the Google Mobile Ads SDK is
/// never initialized at all. No ad requests go out, so none of them can
/// come back "Account not approved yet" or no-fill.
///
/// That means the pacing and gating can be exercised and tuned for real
/// before AdMob approval lands.
///
/// Flipping this to `true` is the only change needed to go live: every
/// placement picks up its real ad unit from [AdService] and the placeholder
/// stops being reachable. Nothing else in the app branches on it.
const bool adsEnabled = false;