增加常量文件，修改作者注释

db/20250427232209_create_users_table.up.sql

@@ -0,0 +1,14 @@
+create sequence public.users_cid_seq
+    as integer;
+
+create table public.users
+(
+    cid            serial
+        constraint users_pk
+        default nextval('users_cid_seq')
+        primary key,
+    password       char(60) not null,
+    first_name     varchar(255),
+    last_name      varchar(255),
+    network_rating smallint not null
+);