Change TEXT to INTEGER in card_stats

sql/card_stats.sql

@@ -5,9 +5,9 @@ create table card_stats
     word_id     INTEGER           not null
         references words
             on delete cascade,
-    set_id      TEXT              not null
+    set_id      INTEGER              not null
         references card_set
             on delete cascade,
     score       INTEGER default 1 not null,
-    last_opened integer           not null
+    last_opened INTEGER           not null
 );