fix(ui): show reset countdown for idle usage windows with known reset time

UsageProgressBar returned 'now' whenever showNowWhenIdle was set and
utilization was 0%, ignoring resetsAt. OpenAI Codex 7d windows at 0%
usage still carry a future reset time, so the admin account list hid it.
Only fall back to 'now' when no reset time is known.

frontend/src/components/account/UsageProgressBar.vue

@@ -188,13 +188,11 @@ const shouldShowResetTime = computed(() => {
 
 // Format reset time
 const formatResetTime = computed(() => {
-  // For rolling windows, when utilization is 0%, treat as immediately available.
-  if (props.showNowWhenIdle && props.utilization <= 0) {
-    return t('usage.resetNow')
+  if (!props.resetsAt) {
+    // Idle rolling window without a known reset time: treat as immediately available.
+    return props.showNowWhenIdle && props.utilization <= 0 ? t('usage.resetNow') : '-'
   }
 
-  if (!props.resetsAt) return '-'
-
   const date = new Date(props.resetsAt)
   const diffMs = date.getTime() - now.value.getTime()
 

frontend/src/components/account/__tests__/UsageProgressBar.spec.ts

@@ -22,7 +22,7 @@ describe('UsageProgressBar', () => {
     vi.useRealTimers()
   })
 
-  it('showNowWhenIdle=true 且利用率为 0 时显示“现在”', () => {
+  it('showNowWhenIdle=true 且利用率为 0 但有未来 resetsAt 时显示倒计时', () => {
     const wrapper = mount(UsageProgressBar, {
       props: {
         label: '5h',
@@ -33,8 +33,8 @@ describe('UsageProgressBar', () => {
       }
     })
 
-    expect(wrapper.text()).toContain('usage.resetNow')
-    expect(wrapper.text()).not.toContain('2h 30m')
+    expect(wrapper.text()).toContain('2h 30m')
+    expect(wrapper.text()).not.toContain('usage.resetNow')
   })
 
   it('showNowWhenIdle=true 但利用率大于 0 时显示倒计时', () => {