perf(finance): 统一把 Intl.DateTimeFormat 提到模块级，消除逐行构造开销

承接 14b595b0。以下 7 处仍在函数体内 `new Intl.DateTimeFormat(...)`，
单次构造约 0.5ms，按行/按条调用时会线性放大：

- utils/finance-date-range.ts         formatShanghaiDate
- utils/http.ts                       （已在上一个提交修复）
- scheduler/cost-finance-sync-job.ts  today
- finance/sales-facts-service.ts      formatDateOnly
- finance/order-refund-service.ts     toChinaDate
- admin/admin-finance-service.ts      chinaDateParts
- admin/admin-dashboard-service.ts    resolveChinaTodayRange
- scripts/sync-cost-finance.ts        formatShanghaiDate

均为同选项的纯 hoist，输出逐字节不变：formatShanghaiDate 用 9 例跨时区/
毫秒/闰日语料与旧实现比对一致；其余为相同 en-CA/en-US + Asia/Shanghai
选项的等价替换，formatToParts 的取值改为单次遍历、去掉 fromEntries/reduce。

apps/backend/scripts/sync-cost-finance.ts

@@ -78,11 +78,14 @@ function normalizeDays(value: unknown) {
   return parsed
 }
 
+/** 模块级只构造一次：`new Intl.DateTimeFormat()` 每次约 0.5ms，逐条调用会线性放大。 */
+const SHANGHAI_DATE_FORMATTER = new Intl.DateTimeFormat('en-CA', {
+  timeZone: 'Asia/Shanghai',
+  year: 'numeric',
+  month: '2-digit',
+  day: '2-digit',
+})
+
 function formatShanghaiDate(value: Date) {
-  return new Intl.DateTimeFormat('en-CA', {
-    timeZone: 'Asia/Shanghai',
-    year: 'numeric',
-    month: '2-digit',
-    day: '2-digit',
-  }).format(value)
+  return SHANGHAI_DATE_FORMATTER.format(value)
 }

apps/backend/src/services/admin/admin-dashboard-service.ts

@@ -63,22 +63,24 @@ export async function getAdminDashboardSummary() {
   }
 }
 
+/** 模块级只构造一次：`new Intl.DateTimeFormat()` 每次约 0.5ms，逐条调用会线性放大。 */
+const CHINA_DAY_PARTS_FORMATTER = new Intl.DateTimeFormat('en-US', {
+  timeZone: 'Asia/Shanghai',
+  year: 'numeric',
+  month: '2-digit',
+  day: '2-digit',
+})
+
 /** 返回中国时区当天对应的 UTC 查询范围，便于使用时间索引。 */
 function resolveChinaTodayRange(now: string) {
-  const parts = new Intl.DateTimeFormat('en-US', {
-    timeZone: 'Asia/Shanghai',
-    year: 'numeric',
-    month: '2-digit',
-    day: '2-digit',
-  })
-    .formatToParts(new Date(now))
-    .reduce<Record<string, string>>((result, part) => {
-      result[part.type] = part.value
-      return result
-    }, {})
-  const year = Number(parts.year || 0)
-  const month = Number(parts.month || 1)
-  const day = Number(parts.day || 1)
+  let year = 0
+  let month = 1
+  let day = 1
+  for (const part of CHINA_DAY_PARTS_FORMATTER.formatToParts(new Date(now))) {
+    if (part.type === 'year') year = Number(part.value)
+    else if (part.type === 'month') month = Number(part.value)
+    else if (part.type === 'day') day = Number(part.value)
+  }
   const todayStart = Date.UTC(year || 0, (month || 1) - 1, day || 1, -8)
   const tomorrowStart = todayStart + 24 * 60 * 60 * 1000
 

apps/backend/src/services/admin/admin-finance-service.ts

@@ -455,15 +455,25 @@ function parseFinanceBoundary(value: string, fallbackDate: string, end: boolean)
     : parsed.toISOString()
 }
 
+/** 模块级只构造一次：`new Intl.DateTimeFormat()` 每次约 0.5ms，逐条调用会线性放大。 */
+const CHINA_DATE_PARTS_FORMATTER = new Intl.DateTimeFormat('en-CA', {
+  timeZone: CHINA_TIME_ZONE,
+  year: 'numeric',
+  month: '2-digit',
+  day: '2-digit',
+})
+
 function chinaDateParts(value: string) {
-  const parts = new Intl.DateTimeFormat('en-CA', {
-    timeZone: CHINA_TIME_ZONE,
-    year: 'numeric',
-    month: '2-digit',
-    day: '2-digit',
-  }).formatToParts(new Date(value))
-  const result = Object.fromEntries(parts.map((part) => [part.type, part.value]))
-  return `${result.year}-${result.month}-${result.day}`
+  const parts = CHINA_DATE_PARTS_FORMATTER.formatToParts(new Date(value))
+  let year = ''
+  let month = ''
+  let day = ''
+  for (const part of parts) {
+    if (part.type === 'year') year = part.value
+    else if (part.type === 'month') month = part.value
+    else if (part.type === 'day') day = part.value
+  }
+  return `${year}-${month}-${day}`
 }
 
 function chinaDateToUtcIso(value: string) {

apps/backend/src/services/finance/order-refund-service.ts

@@ -526,15 +526,18 @@ function normalizeTimestamp(value: unknown): string {
   return date.toISOString()
 }
 
+/** 模块级只构造一次：`new Intl.DateTimeFormat()` 每次约 0.5ms，逐条调用会线性放大。 */
+const CHINA_DATE_FORMATTER = new Intl.DateTimeFormat('en-CA', {
+  timeZone: 'Asia/Shanghai',
+  year: 'numeric',
+  month: '2-digit',
+  day: '2-digit',
+})
+
 function toChinaDate(value: string): string {
   const date = new Date(value)
   if (Number.isNaN(date.getTime())) return ''
-  return new Intl.DateTimeFormat('en-CA', {
-    timeZone: 'Asia/Shanghai',
-    year: 'numeric',
-    month: '2-digit',
-    day: '2-digit',
-  }).format(date)
+  return CHINA_DATE_FORMATTER.format(date)
 }
 
 function formatFen(value: number): string {

apps/backend/src/services/finance/sales-facts-service.ts

@@ -486,14 +486,17 @@ function mapSalesFact(row: SalesFactRow) {
   }
 }
 
+/** 模块级只构造一次：`new Intl.DateTimeFormat()` 每次约 0.5ms，逐行调用会线性放大。 */
+const SHANGHAI_DATE_FORMATTER = new Intl.DateTimeFormat('en-CA', {
+  timeZone: 'Asia/Shanghai',
+  year: 'numeric',
+  month: '2-digit',
+  day: '2-digit',
+})
+
 function formatDateOnly(value: string | Date): string {
   if (value instanceof Date) {
-    return new Intl.DateTimeFormat('en-CA', {
-      timeZone: 'Asia/Shanghai',
-      year: 'numeric',
-      month: '2-digit',
-      day: '2-digit',
-    }).format(value)
+    return SHANGHAI_DATE_FORMATTER.format(value)
   }
   return String(value || '').slice(0, 10)
 }

apps/backend/src/services/scheduler/cost-finance-sync-job.ts

@@ -82,13 +82,16 @@ export async function runCostFinanceSyncJob(job: JsonObject = {}) {
   }
 }
 
+/** 模块级只构造一次：`new Intl.DateTimeFormat()` 每次约 0.5ms，逐条调用会线性放大。 */
+const SHANGHAI_DATE_FORMATTER = new Intl.DateTimeFormat('en-CA', {
+  timeZone: 'Asia/Shanghai',
+  year: 'numeric',
+  month: '2-digit',
+  day: '2-digit',
+})
+
 function today() {
-  return new Intl.DateTimeFormat('en-CA', {
-    timeZone: 'Asia/Shanghai',
-    year: 'numeric',
-    month: '2-digit',
-    day: '2-digit',
-  }).format(new Date())
+  return SHANGHAI_DATE_FORMATTER.format(new Date())
 }
 
 function shiftDays(days: number) {

apps/backend/src/utils/finance-date-range.ts

@@ -40,13 +40,16 @@ export function resolveFinanceDateRange(
   return { fromDate, toDate }
 }
 
+/** 模块级只构造一次：`new Intl.DateTimeFormat()` 每次约 0.5ms，逐条调用会线性放大。 */
+const SHANGHAI_DATE_FORMATTER = new Intl.DateTimeFormat('en-CA', {
+  timeZone: 'Asia/Shanghai',
+  year: 'numeric',
+  month: '2-digit',
+  day: '2-digit',
+})
+
 export function formatShanghaiDate(value: Date): string {
-  return new Intl.DateTimeFormat('en-CA', {
-    timeZone: 'Asia/Shanghai',
-    year: 'numeric',
-    month: '2-digit',
-    day: '2-digit',
-  }).format(value)
+  return SHANGHAI_DATE_FORMATTER.format(value)
 }
 
 export function shiftDate(date: string, days: number): string {