睡眠页默认窗口改为 14 天

30 根堆叠柱在常规宽度下每根约 10px，扣掉段间 2px 间隙后深睡那层
细到难以辨认，悬停命中区也逼近 24px 下限。默认收到 14 天让柱宽
翻倍，更长的窗口仍可手动选择。

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

client/src/pages/Sleep.tsx

@@ -15,7 +15,10 @@ function avg(values: Array<number | null | undefined>): number | null {
 
 function Sleep() {
   const [days, setDays] = useState<HealthDay[]>([]);
-  const [range, setRange] = useState(30);
+  // 14 by default: the stacked chart needs bars wide enough to read the
+  // thinnest stage and to give hover a ~24px hit target. Longer windows stay
+  // available for the trend, where density matters less.
+  const [range, setRange] = useState(14);
   const [loading, setLoading] = useState(true);
   const [error, setError] = useState('');