fix(auth): 长任务活跃期间续期会话

frontend/src/utils/sessionActivity.ts

@@ -0,0 +1,32 @@
+import { ref } from 'vue'
+
+const LOGIN_TIME_STORAGE_KEY = 'loginTime'
+
+function storedActivityTime() {
+  return Number.parseInt(localStorage.getItem(LOGIN_TIME_STORAGE_KEY) || '0', 10) || 0
+}
+
+/**
+ * 会话按“最后活跃时间”计算，而不是从首次登录起固定倒计时。
+ * 该 ref 被认证 store 与请求层共享，确保 API 活动可以立即影响路由守卫。
+ */
+export const sessionActivityTime = ref(storedActivityTime())
+
+export function startSessionActivity() {
+  sessionActivityTime.value = Date.now()
+  localStorage.setItem(LOGIN_TIME_STORAGE_KEY, String(sessionActivityTime.value))
+}
+
+export function touchSessionActivity() {
+  if (!sessionActivityTime.value) return
+  startSessionActivity()
+}
+
+export function syncSessionActivity() {
+  sessionActivityTime.value = storedActivityTime()
+}
+
+export function clearSessionActivity() {
+  sessionActivityTime.value = 0
+  localStorage.removeItem(LOGIN_TIME_STORAGE_KEY)
+}