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/account-pool-ui.js

@@ -0,0 +1,58 @@
+(function attachSidepanelAccountPoolUi(globalScope) {
+  function createAccountPoolFormController(options = {}) {
+    const {
+      formShell = null,
+      toggleButton = null,
+      hiddenLabel = '添加账号',
+      visibleLabel = '取消添加',
+      onClear = null,
+      onFocus = null,
+    } = options;
+
+    let visible = false;
+
+    function sync() {
+      if (formShell) {
+        formShell.hidden = !visible;
+      }
+      if (toggleButton) {
+        toggleButton.textContent = visible ? visibleLabel : hiddenLabel;
+        toggleButton.setAttribute('aria-expanded', String(visible));
+      }
+    }
+
+    function setVisible(nextVisible, controlOptions = {}) {
+      const {
+        clearForm = false,
+        focusField = false,
+      } = controlOptions;
+
+      visible = Boolean(nextVisible);
+      if (clearForm && typeof onClear === 'function') {
+        onClear();
+      }
+
+      sync();
+
+      if (visible && focusField && typeof onFocus === 'function') {
+        onFocus();
+      }
+    }
+
+    function isVisible() {
+      return visible;
+    }
+
+    sync();
+
+    return {
+      isVisible,
+      setVisible,
+      sync,
+    };
+  }
+
+  globalScope.SidepanelAccountPoolUi = {
+    createAccountPoolFormController,
+  };
+})(window);