fix: transactions 테이블에 PK 가 없음

init/sql/000-init.sql

@@ -40,7 +40,7 @@ CREATE TABLE relations (
 );
 
 CREATE TABLE transactions (
-    id                      CHAR(12) NOT NULL,
+    id                      CHAR(12) NOT NULL PRIMARY KEY,
     user_id                 INTEGER NOT NULL
                             CONSTRAINT transaction_user_id REFERENCES "users",
     combination_id          INTEGER NULL