fix(ui): 修復日期控件時區展示偏移 Bug，並修正負成本的格式化顯示

Memory.md

@@ -35,7 +35,7 @@
 - 重构 `<SyncButton />` 并将其提升至 Dashboard 首页，实现总资产大盘的全局一键实盘刷新。
 
 ## 修复记录
-- 修复了全局时区偏移问题，并解决了日期控件手动输入导致的崩溃 Bug。在 `src/libs/utils.ts` 中新增 `nowInShanghai()`、`formatDateForDatetimeLocal()` 和 `parseDateTimeLocalToUTC_v2()` 函数，强制使用 `Asia/Shanghai` (UTC+8) 时区。所有 `new Date()` 调用（包括 Server Actions）均已对齐至东八区。日期选择器增加字符串格式校验与解析逻辑，避免 `Invalid time value` 错误。
+- 解决了日期选择控件的时区偏移 Bug，确保全球通用：在 `src/libs/utils.ts` 中重写 `formatDateForDatetimeLocal()` 与 `parseDateTimeLocalToUTC_v2()` 函数，采用 `Intl.DateTimeFormat` 动态获取 `Asia/Shanghai` 时区偏移量，确保 UTC 时间到本地时间的双向转换精确无误，修复了用户选 10 点展示为 2 点的问题。修正了前端数据格式化逻辑，在 `src/lib/formatters.ts` 中增加空值/NaN 兜底处理，在 `src/app/dashboard/page.tsx` 中将平均成本与摊薄成本的显示条件从 `.gt(0)` 改为 `.ne(0)`，支持英特尔负成本等极端场景下的精确数字展示。
 
 ## 资产分布图表按市场维度升级 (Task 32)
 - 优化资产分布图表，升级为按市场维度聚合展示，并增强了 Tooltip 的颜色指代与明细交互。

app/dashboard/page.tsx

@@ -71,8 +71,8 @@ export default async function DashboardPage() {
             const posPnlNative = new Big(pos.pnlNative);
             const posPnlNativePositive = posPnlNative.gte(0);
 
-            const avgCostFormatted = new Big(pos.avgCost).gt(0) ? formatAmount(pos.avgCost) : '-';
+            const avgCostFormatted = new Big(pos.avgCost).ne(0) && pos.avgCost !== '0' ? formatAmount(pos.avgCost) : '-';
-            const dilutedCostFormatted = new Big(pos.dilutedCost).gt(0) ? formatAmount(pos.dilutedCost) : '-';
+            const dilutedCostFormatted = new Big(pos.dilutedCost).ne(0) && pos.dilutedCost !== '0' ? formatAmount(pos.dilutedCost) : '-';
 
             return (
               <Card key={pos.assetId}>

src/lib/formatters.ts

@@ -1,7 +1,11 @@
 import Big from 'big.js';
 
 export function formatAmount(value: string): string {
-  return new Big(value).toFixed(2);
+  if (value === null || value === undefined || value === '' || isNaN(Number(value))) {
+    return '-';
+  }
+  const result = new Big(value).toFixed(2);
+  return result;
 }
 
 export function formatQuantity(value: string, assetType: string): string {

src/libs/utils.ts

@@ -1,6 +1,5 @@
 import { type ClassValue, clsx } from "clsx"
 import { twMerge } from "tailwind-merge"
-import { toZonedTime, fromZonedTime } from "date-fns-tz"
 
 const TIMEZONE = "Asia/Shanghai"
 
@@ -8,6 +7,53 @@ export function cn(...inputs: ClassValue[]) {
   return twMerge(clsx(inputs))
 }
 
+function getShanghaiOffsetMs(): number {
+  const formatter = new Intl.DateTimeFormat("en-US", {
+    timeZone: TIMEZONE,
+    timeZoneName: "short",
+  })
+  const parts = formatter.formatToParts(new Date())
+  const tzPart = parts.find((p) => p.type === "timeZoneName")
+  if (!tzPart) return 8 * 60 * 60 * 1000
+
+  const match = tzPart.value.match(/^([+-])(\d{2}):?(\d{2})$/)
+  if (!match) return 8 * 60 * 60 * 1000
+
+  const sign = match[1] === "+" ? 1 : -1
+  const offsetHours = parseInt(match[2], 10)
+  const offsetMinutes = parseInt(match[3], 10)
+  return sign * (offsetHours * 60 + offsetMinutes) * 60 * 1000
+}
+
+export function formatDateForDatetimeLocal(date: Date): string {
+  const shanghaiOffsetMs = getShanghaiOffsetMs()
+  const localTimeMs = date.getTime() + shanghaiOffsetMs
+  const localDate = new Date(localTimeMs)
+
+  const year = localDate.getUTCFullYear()
+  const month = String(localDate.getUTCMonth() + 1).padStart(2, "0")
+  const day = String(localDate.getUTCDate()).padStart(2, "0")
+  const hours = String(localDate.getUTCHours()).padStart(2, "0")
+  const minutes = String(localDate.getUTCMinutes()).padStart(2, "0")
+  return `${year}-${month}-${day}T${hours}:${minutes}`
+}
+
+export function parseDateTimeLocalToUTC_v2(year: number, month: number, day: number, hours: number, minutes: number): Date {
+  const localTimeMs = Date.UTC(year, month, day, hours, minutes)
+  const shanghaiOffsetMs = getShanghaiOffsetMs()
+  const utcMs = localTimeMs - shanghaiOffsetMs
+  return new Date(utcMs)
+}
+
+export function parseDateTimeLocalToUTC(value: string): Date | null {
+  if (!value) return null
+  const [datePart, timePart] = value.split("T")
+  if (!datePart) return null
+  const [y, m, d] = datePart.split("-").map(Number)
+  const [h = 0, min = 0] = timePart ? timePart.split(":").map(Number) : [0, 0]
+  return parseDateTimeLocalToUTC_v2(y, m - 1, d, h, min)
+}
+
 export function nowInShanghai(): Date {
   const now = new Date()
   const utcStr = now.toLocaleString("en-US", { timeZone: "UTC" })