fix(ui): show 'now' for idle OpenAI usage windows

Use utilization-based idle detection instead of local request counts so newly imported OAuth accounts keep countdowns when usage is non-zero.

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

@@ -0,0 +1,69 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
+import { mount } from '@vue/test-utils'
+import UsageProgressBar from '../UsageProgressBar.vue'
+
+vi.mock('vue-i18n', async () => {
+  const actual = await vi.importActual<typeof import('vue-i18n')>('vue-i18n')
+  return {
+    ...actual,
+    useI18n: () => ({
+      t: (key: string) => key
+    })
+  }
+})
+
+describe('UsageProgressBar', () => {
+  beforeEach(() => {
+    vi.useFakeTimers()
+    vi.setSystemTime(new Date('2026-03-17T00:00:00Z'))
+  })
+
+  afterEach(() => {
+    vi.useRealTimers()
+  })
+
+  it('showNowWhenIdle=true 且利用率为 0 时显示“现在”', () => {
+    const wrapper = mount(UsageProgressBar, {
+      props: {
+        label: '5h',
+        utilization: 0,
+        resetsAt: '2026-03-17T02:30:00Z',
+        showNowWhenIdle: true,
+        color: 'indigo'
+      }
+    })
+
+    expect(wrapper.text()).toContain('现在')
+    expect(wrapper.text()).not.toContain('2h 30m')
+  })
+
+  it('showNowWhenIdle=true 但利用率大于 0 时显示倒计时', () => {
+    const wrapper = mount(UsageProgressBar, {
+      props: {
+        label: '7d',
+        utilization: 12,
+        resetsAt: '2026-03-17T02:30:00Z',
+        showNowWhenIdle: true,
+        color: 'emerald'
+      }
+    })
+
+    expect(wrapper.text()).toContain('2h 30m')
+    expect(wrapper.text()).not.toContain('现在')
+  })
+
+  it('showNowWhenIdle=false 时保持原有倒计时行为', () => {
+    const wrapper = mount(UsageProgressBar, {
+      props: {
+        label: '1d',
+        utilization: 0,
+        resetsAt: '2026-03-17T02:30:00Z',
+        showNowWhenIdle: false,
+        color: 'indigo'
+      }
+    })
+
+    expect(wrapper.text()).toContain('2h 30m')
+    expect(wrapper.text()).not.toContain('现在')
+  })
+})