feat: 优化按钮样式，调整邮箱获取按钮和保存设置按钮的内边距和缩放行为

sidepanel/sidepanel.css

@@ -334,13 +334,10 @@ header {
   background: var(--bg-hover);
 }
 
-#btn-fetch-email {
-  padding-inline: 10px;
-}
-
+#btn-fetch-email,
 #btn-save-settings {
-  min-width: 58px;
   padding-inline: 10px;
+  flex-shrink: 0;
 }
 
 .data-select {