fix: 后端代码格式化

backend/src/main/java/com/openisle/service/EmailSender.java

@@ -4,11 +4,12 @@ package com.openisle.service;
  * Abstract email sender used to deliver emails.
  */
 public abstract class EmailSender {
-    /**
-     * Send an email to a recipient.
-     * @param to recipient email address
-     * @param subject email subject
-     * @param text email body
-     */
-    public abstract void sendEmail(String to, String subject, String text);
+
+  /**
+   * Send an email to a recipient.
+   * @param to recipient email address
+   * @param subject email subject
+   * @param text email body
+   */
+  public abstract void sendEmail(String to, String subject, String text);
 }