fix(sleep): one day total for every sleep reader, and the latest night is a night

A day's sleep is the main night plus its naps (daySleepMinutes). The
series, the sleep score and the composition already read it that way; the
sleep list, the CSV export and the correlation sleep channel read the main
night alone, so a day of naps listed as 0 h and an average over the list
counted it as a night without sleep. The list now carries the day total in
value and the main night alone in the new mainAsleepMinutes field; the nap
caption reads as included.

GET /api/sleep/night without a date answered the latest day holding any
sleep, so a nap after the last night left the hypnogram with no night to
draw. It now walks back to the latest night with a main sleep; nap days
stay reachable by date.

The SQL night page bounded a night by its asleep sessions only, so an
in-bed-only session of the same night fell outside a chunked read that the
one-night read counted. The span now covers every session of the night.

src/lib/analytics/sleep-night.ts

@@ -1282,6 +1282,24 @@ export function separateNightsAndNaps(
   return days.sort((a, b) => a.night.localeCompare(b.night));
 }
 
+/**
+ * A wake day's sleep total, the one definition every reader states: the main
+ * night plus every nap of the day. It equals `SleepNight.asleepMinutes` for
+ * the same rows (both sum each session's canonical-writer asleep minutes),
+ * which is what the series, the sleep score and the composition read; the
+ * main night alone stays available as `main.asleepMinutes` /
+ * `SleepNight.mainSession`. A day of naps alone totals its naps, not 0.
+ */
+export function daySleepMinutes(day: {
+  main: SleepSession | null;
+  naps: readonly SleepSession[];
+}): number {
+  return (
+    (day.main?.asleepMinutes ?? 0) +
+    day.naps.reduce((sum, nap) => sum + nap.asleepMinutes, 0)
+  );
+}
+
 export interface SleepNightSummary {
   /**
    * A `DataSummary` whose every value is a per-night TIME-ASLEEP total