refactor: extract formatCompactNumber util and add last_used_at to refresh key

- Add formatCompactNumber() for consistent large-number formatting (K/M/B)
- Include last_used_at in OpenAI usage refresh key for better change detection
- Add .gitattributes eol=lf rules for frontend source files

.gitattributes

@@ -4,6 +4,13 @@ backend/migrations/*.sql text eol=lf
 # Go 源代码文件
 *.go text eol=lf
 
+# 前端 源代码文件
+*.ts text eol=lf
+*.tsx text eol=lf
+*.js text eol=lf
+*.jsx text eol=lf
+*.vue text eol=lf
+
 # Shell 脚本
 *.sh text eol=lf
 

frontend/src/utils/__tests__/accountUsageRefresh.spec.ts

@@ -8,6 +8,7 @@ describe('buildOpenAIUsageRefreshKey', () => {
       platform: 'openai',
       type: 'oauth',
       updated_at: '2026-03-07T10:00:00Z',
+      last_used_at: '2026-03-07T09:59:00Z',
       extra: {
         codex_usage_updated_at: '2026-03-07T10:00:00Z',
         codex_5h_used_percent: 0,
@@ -27,12 +28,35 @@ describe('buildOpenAIUsageRefreshKey', () => {
     expect(buildOpenAIUsageRefreshKey(base)).not.toBe(buildOpenAIUsageRefreshKey(next))
   })
 
+  it('会在 last_used_at 变化时生成不同 key', () => {
+    const base = {
+      id: 3,
+      platform: 'openai',
+      type: 'oauth',
+      updated_at: '2026-03-07T10:00:00Z',
+      last_used_at: '2026-03-07T10:00:00Z',
+      extra: {
+        codex_usage_updated_at: '2026-03-07T10:00:00Z',
+        codex_5h_used_percent: 12,
+        codex_7d_used_percent: 24
+      }
+    } as any
+
+    const next = {
+      ...base,
+      last_used_at: '2026-03-07T10:02:00Z'
+    }
+
+    expect(buildOpenAIUsageRefreshKey(base)).not.toBe(buildOpenAIUsageRefreshKey(next))
+  })
+
   it('非 OpenAI OAuth 账号返回空 key', () => {
     expect(buildOpenAIUsageRefreshKey({
       id: 2,
       platform: 'anthropic',
       type: 'oauth',
       updated_at: '2026-03-07T10:00:00Z',
+      last_used_at: '2026-03-07T10:00:00Z',
       extra: {}
     } as any)).toBe('')
   })

frontend/src/utils/__tests__/formatCompactNumber.spec.ts

@@ -0,0 +1,22 @@
+import { describe, expect, it } from 'vitest'
+import { formatCompactNumber } from '../format'
+
+describe('formatCompactNumber', () => {
+  it('formats boundary values with K/M/B', () => {
+    expect(formatCompactNumber(0)).toBe('0')
+    expect(formatCompactNumber(999)).toBe('999')
+    expect(formatCompactNumber(1000)).toBe('1.0K')
+    expect(formatCompactNumber(999999)).toBe('1000.0K')
+    expect(formatCompactNumber(1000000)).toBe('1.0M')
+    expect(formatCompactNumber(1000000000)).toBe('1.0B')
+  })
+
+  it('supports disabling billion unit (requests style)', () => {
+    expect(formatCompactNumber(1000000000, { allowBillions: false })).toBe('1000.0M')
+  })
+
+  it('returns 0 for nullish input', () => {
+    expect(formatCompactNumber(null)).toBe('0')
+    expect(formatCompactNumber(undefined)).toBe('0')
+  })
+})

frontend/src/utils/accountUsageRefresh.ts

@@ -5,7 +5,7 @@ const normalizeUsageRefreshValue = (value: unknown): string => {
   return String(value)
 }
 
-export const buildOpenAIUsageRefreshKey = (account: Pick<Account, 'id' | 'platform' | 'type' | 'updated_at' | 'rate_limit_reset_at' | 'extra'>): string => {
+export const buildOpenAIUsageRefreshKey = (account: Pick<Account, 'id' | 'platform' | 'type' | 'updated_at' | 'last_used_at' | 'rate_limit_reset_at' | 'extra'>): string => {
   if (account.platform !== 'openai' || account.type !== 'oauth') {
     return ''
   }
@@ -14,6 +14,7 @@ export const buildOpenAIUsageRefreshKey = (account: Pick<Account, 'id' | 'platfo
   return [
     account.id,
     account.updated_at,
+    account.last_used_at,
     account.rate_limit_reset_at,
     extra.codex_usage_updated_at,
     extra.codex_5h_used_percent,

frontend/src/utils/format.ts

@@ -247,6 +247,26 @@ export function formatTokensK(tokens: number): string {
   return tokens.toString()
 }
 
+/**
+ * 格式化大数字（K/M/B，保留 1 位小数）
+ * @param num 数字
+ * @param options allowBillions=false 时最高只显示到 M
+ */
+export function formatCompactNumber(
+  num: number | null | undefined,
+  options?: { allowBillions?: boolean }
+): string {
+  if (num === null || num === undefined) return '0'
+
+  const abs = Math.abs(num)
+  const allowBillions = options?.allowBillions !== false
+
+  if (allowBillions && abs >= 1_000_000_000) return `${(num / 1_000_000_000).toFixed(1)}B`
+  if (abs >= 1_000_000) return `${(num / 1_000_000).toFixed(1)}M`
+  if (abs >= 1_000) return `${(num / 1_000).toFixed(1)}K`
+  return num.toString()
+}
+
 /**
  * 格式化倒计时（从现在到目标时间的剩余时间）
  * @param targetDate 目标日期字符串或 Date 对象