feat(桌面与监控): 完善工作台导航和登录活动定位

- 优化桌面标签、上下文标题、前进后退、导航栏隐藏和原生菜单体验

- 补充登录会话 IP 采集、地理位置回退、管理端展示及数据库迁移

- 更新桌面发布检查、运维文档和前后端测试覆盖

frontend/src/views/DesktopPreferences.vue

@@ -313,6 +313,7 @@ const desktopUpdateStatus = ref<DesktopUpdateStatusSnapshot>(getDesktopUpdateSta
 let updateStatusUnlisten: (() => void) | undefined;
 let connectionPendingTimer: number | undefined;
 const themeOptions = [
+  { value: "system" as const, label: "跟随系统", icon: Monitor },
   { value: "light" as const, label: "明亮", icon: Sunny },
   { value: "dark" as const, label: "暗黑", icon: Moon },
 ];
@@ -1358,7 +1359,9 @@ h3 {
  * ===================================================== */
 .theme-segmented {
   display: inline-grid;
-  grid-template-columns: repeat(2, minmax(72px, 1fr));
+  grid-template-columns: repeat(3, minmax(0, 1fr));
+  flex: 0 1 336px;
+  width: min(100%, 336px);
   gap: 3px;
   padding: 3px;
   border: 1px solid var(--pref-border-card);
@@ -1372,7 +1375,7 @@ h3 {
   align-items: center;
   justify-content: center;
   gap: 6px;
-  min-width: 72px;
+  min-width: 0;
   height: 28px;
   padding: 0 10px;
   border: 0;
@@ -1383,6 +1386,7 @@ h3 {
   font: inherit;
   font-size: 12px;
   font-weight: 600;
+  white-space: nowrap;
   transition:
     background-color 140ms ease,
     color 140ms ease,