Update purchases table

sql/purchases.sql

@@ -4,10 +4,9 @@ CREATE TABLE IF NOT EXISTS purchases(
     user_id UUID NOT NULL REFERENCES users(id),
     stripe_id TEXT NOT NULL,
     status TEXT NOT NULL,
-    token_packs INT NOT NULL,
+    pack_count INT NOT NULL,
     cost_per_pack INT NOT NULL,
-    tokens_purchased INT NOT NULL,
-    cost INT NOT NULL,
+    tokens_per_pack INT NOT NULL,
     created_at TIMESTAMPTZ NOT NULL
 );