fix(mail2925): 修复验证码轮询与登录态复用逻辑并清理中文文案，重构 sidepanel：统一 Hotmail 和 2925 号池表单交互

- 抽出共享 account-pool-ui helper
- 统一添加账号、取消添加、批量导入交互
- 调整号池列表收起高度与按钮布局
- 补充测试并同步更新项目文档

sidepanel/sidepanel.css

@@ -1112,17 +1112,17 @@ header {
   visibility: hidden;
 }
 
-.mail2925-form-shell {
+.account-pool-form-shell {
   display: flex;
   flex-direction: column;
   gap: 10px;
 }
 
-.mail2925-actions-inline {
+.account-pool-actions-inline {
   width: 100%;
 }
 
-.mail2925-import-action {
+.account-pool-import-action {
   margin-left: auto;
 }
 
@@ -1148,7 +1148,7 @@ header {
 }
 
 .hotmail-list-shell.is-collapsed {
-  max-height: 236px;
+  max-height: 176px;
 }
 
 .hotmail-list-shell.is-expanded {