feat: 顶栏按钮支持位置选择（header/user-dropdown/none）

为顶栏所有部件按钮添加独立的位置配置，支持在顶栏、用户下拉菜单、不显示
三种选项间切换，每个按钮可独立设置。

- 新增 7 个位置偏好字段：globalSearchButtonPosition、
  themeToggleButtonPosition、languageToggleButtonPosition、
  fullscreenButtonPosition、notificationButtonPosition、
  refreshButtonPosition、timezoneButtonPosition
- 合并 lockScreenButtonPosition、logoutButtonPosition
- header.vue 按位置条件过滤按钮显示
- user-dropdown.vue 新增对应菜单项，支持在用户下拉菜单中显示
- 偏好设置界面仅保留位置选择器（不再需要独立的开关）
- 更新中英文国际化文案

Co-Authored-By: AtomCode (deepseek-v4-flash) <noreply@atomgit.com>

packages/locales/src/langs/en-US/common.json

@@ -21,5 +21,6 @@
   "yes": "Yes",
   "no": "No",
   "showSearchPanel": "Show search panel",
-  "hideSearchPanel": "Hide search panel"
+  "hideSearchPanel": "Hide search panel",
+  "notShow": "Don't Show"
 }

packages/locales/src/langs/en-US/preferences.json

@@ -193,14 +193,25 @@
   "widget": {
     "title": "Widget",
     "globalSearch": "Enable Global Search",
+    "globalSearchPosition": "Global Search Position",
     "fullscreen": "Enable Fullscreen",
+    "fullscreenPosition": "Fullscreen Position",
     "themeToggle": "Enable Theme Toggle",
+    "themeTogglePosition": "Theme Toggle Position",
     "languageToggle": "Enable Language Toggle",
+    "languageTogglePosition": "Language Toggle Position",
     "notification": "Enable Notification",
+    "notificationPosition": "Notification Position",
     "sidebarToggle": "Enable Sidebar Toggle",
     "lockScreen": "Enable Lock Screen",
+    "lockScreenPosition": "Lock Screen Button Position",
+    "logoutButtonPosition": "Logout Button Position",
+    "header": "Header",
+    "userDropdown": "User Dropdown",
     "refresh": "Enable Refresh",
-    "timezone": "Enable Timezone"
+    "refreshPosition": "Refresh Position",
+    "timezone": "Enable Timezone",
+    "timezonePosition": "Timezone Position"
   },
   "antd": {
     "tabLabel": "Antd Extension",

packages/locales/src/langs/zh-CN/common.json

@@ -21,5 +21,6 @@
   "yes": "是",
   "no": "否",
   "showSearchPanel": "显示搜索面板",
-  "hideSearchPanel": "隐藏搜索面板"
+  "hideSearchPanel": "隐藏搜索面板",
+  "notShow": "不显示"
 }

packages/locales/src/langs/zh-CN/preferences.json

@@ -193,14 +193,25 @@
   "widget": {
     "title": "小部件",
     "globalSearch": "启用全局搜索",
+    "globalSearchPosition": "全局搜索位置",
     "fullscreen": "启用全屏",
+    "fullscreenPosition": "全屏按钮位置",
     "themeToggle": "启用主题切换",
+    "themeTogglePosition": "主题切换位置",
     "languageToggle": "启用语言切换",
+    "languageTogglePosition": "语言切换位置",
     "notification": "启用通知",
+    "notificationPosition": "通知位置",
     "sidebarToggle": "启用侧边栏切换",
     "lockScreen": "启用锁屏",
+    "lockScreenPosition": "锁屏按钮位置",
+    "logoutButtonPosition": "退出按钮位置",
+    "header": "顶栏",
+    "userDropdown": "用户下拉窗",
     "refresh": "启用刷新",
-    "timezone": "启用时区"
+    "refreshPosition": "刷新按钮位置",
+    "timezone": "启用时区",
+    "timezonePosition": "时区按钮位置"
   },
   "antd": {
     "tabLabel": "Antd 拓展",