fix(data): reject stale reschedule snapshots

src/GmRelay.Bot/Migrations/V029__add_completed_game_portfolios_and_reviews.sql

@@ -128,6 +128,12 @@ BEGIN
     WHERE s.id = NEW.id;
 
     IF final_scheduled_at >= now() THEN
+        IF current_setting('transaction_isolation') <> 'read committed' THEN
+            RAISE EXCEPTION
+                'portfolio future reschedule requires read committed isolation'
+                USING ERRCODE = '0A000';
+        END IF;
+
         PERFORM pg.id
         FROM portfolio_games pg
         WHERE EXISTS (