Ad and purchases enabled (still need actual testing)

lib/services/db_schema.dart

@@ -28,6 +28,26 @@ const createFuelEntriesTableSql = '''
 const createFuelEntriesIndexSql =
     'CREATE INDEX idx_fuel_entries_vehicle_id ON fuel_entries(vehicle_id)';
 
+/// A single-row table (`id` is always `1`) holding the furthest-known
+/// "ads disabled until" date from the one-time "remove ads for a year"
+/// purchase — see `PurchaseService`/`AppState.adsCurrentlyDisabled`.
+///
+/// This exists as its own synced table (rather than, say, a
+/// SharedPreferences value) specifically so it survives an app
+/// reinstall: the purchase itself is a *consumable* Play Store product
+/// (needed so it can be bought again once the year lapses), and Play
+/// Store has no memory of a consumed purchase to "restore" — this table,
+/// merged through the same cloud sync as vehicles/fuel_entries, is what
+/// lets a user with cloud sync configured get their remaining ad-free
+/// time back after reinstalling, instead of losing it.
+const createAdFreeEntitlementTableSql = '''
+  CREATE TABLE ad_free_entitlement (
+    id INTEGER PRIMARY KEY CHECK (id = 1),
+    ad_free_until INTEGER,
+    updated_at INTEGER NOT NULL
+  )
+''';
+
 /// Selects fuel entries whose receipt photo still needs uploading to
 /// Drive. Deliberately requires `receipt_drive_file_id IS NULL`, not just
 /// "has a local path": once a row is uploaded, its local copy may still be
@@ -75,3 +95,18 @@ const mergeFuelEntriesSql = '''
   LEFT JOIN main.fuel_entries l ON l.id = r.id
   WHERE l.id IS NULL OR r.updated_at > l.updated_at
 ''';
+
+/// Same "newest `updated_at` wins" rule as [mergeVehiclesSql], applied to
+/// the single `id = 1` entitlement row instead of many rows — whichever
+/// device most recently purchased (or already had) a further-out
+/// `ad_free_until` date wins, so this can never make an entitlement
+/// *shorter* by merging in a stale copy from a device that hasn't synced
+/// in a while.
+const mergeAdFreeEntitlementSql = '''
+  INSERT OR REPLACE INTO main.ad_free_entitlement
+    (id, ad_free_until, updated_at)
+  SELECT r.id, r.ad_free_until, r.updated_at
+  FROM remote_db.ad_free_entitlement r
+  LEFT JOIN main.ad_free_entitlement l ON l.id = r.id
+  WHERE l.id IS NULL OR r.updated_at > l.updated_at
+''';