order by downloaded time to improve ebs read performance

pipeline/01_cc_index/schema.sql

@@ -13,6 +13,7 @@ CREATE TABLE IF NOT EXISTS hosts (
     html_title TEXT,
     iframe_allowed BOOLEAN,
     best_icon_hash TEXT,
+    icon_downloaded_at TIMESTAMPTZ,
     parsed BOOLEAN DEFAULT FALSE,
     random_order DOUBLE PRECISION DEFAULT random()
 );