fix(charts): keep a chart's window open to the end of today

A chart showing the last N days fixed its window end at the mount
instant. The query key kept that bound, so the refetch after a new
reading asked for the same old window and the reading stayed hidden
until the range tab was switched. The window now ends at the end of
the current day in the profile time zone (openEndedFetchWindow, keyed
on the day): every reading saved today falls inside it, the cache key
stays the same all day, and it moves on after midnight. The dashboard
batch shares the end-of-day helper.

Refs #1102

src/components/charts/health-chart.tsx

@@ -2,6 +2,10 @@
 
 import { chartSeriesParams } from "@/components/charts/chart-series-request";
 import { DEFAULT_TIMEZONE } from "@/lib/tz/format";
+import {
+  localDayKeyFor,
+  openEndedFetchWindow,
+} from "@/lib/charts/fetch-window";
 import { keepPreviousData, useQuery } from "@tanstack/react-query";
 import { useAuth } from "@/hooks/use-auth";
 import { useRecordCapabilities } from "@/hooks/use-record-capabilities";
@@ -750,8 +754,14 @@ export function HealthChart({
   // across the whole history (downsampled by tier) rather than the most
   // recent ~365 daily buckets. The client folds those coarse buckets and
   // `bucketTimeSeries` re-buckets to the visible range as before.
+  //
+  // The window ends at the end of TODAY in the profile time zone, not at the
+  // mount instant: a reading saved after the chart mounted (measuredAt = now)
+  // has to fall inside the window the invalidated query refetches. `todayKey`
+  // re-derives on every render, so the window stays put all day (a stable
+  // cache key) and moves on by itself after midnight.
+  const todayKey = localDayKeyFor(new Date(), userTimezone);
   const fetchWindow = useMemo(() => {
-    const to = new Date();
     const windowDays = rangePoints > 0 ? rangePoints : ALL_RANGE_DAYS;
     const compareShift =
       effectiveCompareBaseline === "lastMonth"
@@ -759,17 +769,12 @@ export function HealthChart({
         : effectiveCompareBaseline === "lastYear"
           ? 365
           : 0;
-    const totalDays = windowDays + compareShift;
-    const from = new Date(to.getTime() - totalDays * 86_400_000);
-    // Use ISO strings so the cache key is stable across the day; the
-    // server treats `to` as the upper bound and the chart re-applies the
-    // same day window client-side (see `visibleSlice`).
-    return {
-      from: from.toISOString(),
-      to: to.toISOString(),
-      windowDays: totalDays,
-    };
-  }, [rangePoints, effectiveCompareBaseline]);
+    return openEndedFetchWindow(
+      windowDays + compareShift,
+      todayKey,
+      userTimezone,
+    );
+  }, [rangePoints, effectiveCompareBaseline, userTimezone, todayKey]);
 
   // v1.18.6 — honour the dashboard's batched slice ONLY for windows over
   // 7 days and ONLY when EVERY non-sleep type the chart renders is present