feat: auto-detect user timezone in system settings

Automatically detect and use user's system timezone when no timezone preference is saved. Falls back to 'Asia/Shanghai' if detection fails.

apps/jingrow/frontend/src/shared/utils/timezone.ts

@@ -2,11 +2,35 @@
  * 时区工具函数
  */
 
+/**
+ * 获取用户系统时区
+ * 使用浏览器 API 自动检测用户当前所在时区
+ */
+export function getUserSystemTimezone(): string {
+  try {
+    // 使用 Intl API 获取用户系统时区
+    const systemTimezone = Intl.DateTimeFormat().resolvedOptions().timeZone
+    if (systemTimezone) {
+      return systemTimezone
+    }
+  } catch (error) {
+    console.warn('Failed to get user system timezone:', error)
+  }
+  // 如果获取失败，返回默认时区
+  return 'Asia/Shanghai'
+}
+
 /**
  * 获取当前设置的时区
+ * 优先使用用户保存的时区设置，如果没有则自动获取用户系统时区
  */
 export function getCurrentTimezone(): string {
-  return localStorage.getItem('timezone') || 'Asia/Shanghai'
+  const savedTimezone = localStorage.getItem('timezone')
+  if (savedTimezone) {
+    return savedTimezone
+  }
+  // 如果没有保存的时区，自动获取用户系统时区
+  return getUserSystemTimezone()
 }
 
 /**

apps/jingrow/frontend/src/views/settings/Settings.vue

@@ -210,6 +210,7 @@ import { Icon } from '@iconify/vue'
 import { getCurrentLocale, setLocale, locales, initLocale, t } from '../../shared/i18n'
 import { useAuthStore } from '../../shared/stores/auth'
 import { getEnvironmentConfig, updateEnvironmentConfig, restartEnvironment, type EnvironmentConfig } from '../../shared/api/system'
+import { getCurrentTimezone } from '../../shared/utils/timezone'
 
 const message = useMessage()
 const dialog = useDialog()
@@ -236,7 +237,7 @@ const systemSettings = reactive({
   appName: localStorage.getItem('appName') || 'Jingrow',
   language: getCurrentLocale(),
   itemsPerPage: parseInt(localStorage.getItem('itemsPerPage') || '10'),
-  timezone: localStorage.getItem('timezone') || 'Asia/Shanghai'
+  timezone: getCurrentTimezone()
 })
 
 // 语言选项