feat: re-enable nickname editing in user profile

- Restore nickname field in modify.php SQL update query
- Remove disabled attribute from nickname input in modifypage.php template
- Allow users to update their nickname through profile modification
- Maintain existing HTML entity encoding for security

web/modify.php

@@ -89,14 +89,14 @@ $school = (htmlentities($school, ENT_QUOTES, "UTF-8"));
 $email = (htmlentities($email, ENT_QUOTES, "UTF-8"));
 $sql = "UPDATE `users` SET"
 	. "`password`=?,"
-	// . "`nick`=?,"    //删除此行和81行含的,$nick禁用昵称修改
+	. "`nick`=?,"
 	. "`school`=?,"
 	. "`email`=?"
 	. "WHERE `user_id`=?"
 ;
 //echo $sql;
 //exit(0);
-pdo_query($sql, $password, /*$nick,*/ $school, $email, $user_id);
+pdo_query($sql, $password, $nick, $school, $email, $user_id);
 // if ($nick != "") {
 // 	$sql = "update solution set nick=? where user_id=?";
 // 	pdo_query($sql, $nick, $user_id);