fix: 修复调用趋势统计与图表渲染,柱状图改为平滑折线图

- 趋势窗口 off-by-one:窗口不含当天,当天调用永远不进图表;
  改为以 UTC 日界、包含今天的 N 天窗口
- BarChart 容器 items-end 导致列高塌缩,柱子百分比高度恒为 0,
  图表自组件抽取以来从未渲染;重写为 LineChart(单调三次样条
  平滑曲线 + 面积填充 + 十字线 tooltip + 键盘导航)
- nginx 为 index.html 增加 no-cache、/assets/ 增加 immutable
  缓存,避免发版后浏览器沿用旧 bundle

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

packages/server/src/lib/trends.ts

@@ -8,10 +8,15 @@ export type TrendRow = {
   tokens: bigint;
 };
 
+/**
+ * UTC midnight `days - 1` days ago, so a window of `days` buckets ends on
+ * (and includes) today. UTC is used because `calledAt` is stored as naive
+ * UTC and the SQL groups by its date part.
+ */
 export function daysWindowStart(days: number): Date {
-  const since = new Date();
-  since.setDate(since.getDate() - days);
-  since.setHours(0, 0, 0, 0);
+  const now = new Date();
+  const since = new Date(Date.UTC(now.getUTCFullYear(), now.getUTCMonth(), now.getUTCDate()));
+  since.setUTCDate(since.getUTCDate() - (days - 1));
   return since;
 }
 
@@ -43,7 +48,7 @@ export async function getDailyTrends(opts: { since: Date; days: number; projectI
   const filled = [];
   for (let i = 0; i < days; i++) {
     const d = new Date(since);
-    d.setDate(d.getDate() + i);
+    d.setUTCDate(d.getUTCDate() + i);
     const key = d.toISOString().slice(0, 10);
     const row = map.get(key);
     const total = row ? Number(row.total) : 0;