fix(i18n): sleep headline suffix translates across all six locales

The 'per night' caption beneath the sleep headline was branching on
`locale === "de"` and falling through to English for FR/IT/ES/PL.
Move the string into `insights.sleep.headlineCaptionSuffix` with
native translations (de: pro Nacht, fr: par nuit, it: per notte,
es: por noche, pl: na noc) and resolve it through `t()`.

messages/de.json

@@ -1081,6 +1081,7 @@
       "description": "Phasen-Aufschlüsselung und nächtliche Dauer – gezogen aus Apple Health.",
       "headlineTitle": "Durchschnitt pro Nacht",
       "headlineCaption": "Gemittelt über {count} Nächte – {suffix}",
+      "headlineCaptionSuffix": "pro Nacht",
       "compositionTitle": "Phasen-Verteilung",
       "compositionSubtitle": "Letzte {nights} Nächte",
       "compositionAriaLabel": "Schlafphasen-Verteilung über {nights} Nächte",

messages/en.json

@@ -1081,6 +1081,7 @@
       "description": "Stage breakdown and nightly duration, drawn from Apple Health.",
       "headlineTitle": "Average per night",
       "headlineCaption": "Averaged across {count} nights — {suffix}",
+      "headlineCaptionSuffix": "per night",
       "compositionTitle": "Stage composition",
       "compositionSubtitle": "Last {nights} nights",
       "compositionAriaLabel": "Sleep stage composition over {nights} nights",

messages/es.json

@@ -1081,6 +1081,7 @@
       "description": "Stage breakdown and nightly duration, drawn from Apple Health.",
       "headlineTitle": "Average per night",
       "headlineCaption": "Averaged across {count} nights — {suffix}",
+      "headlineCaptionSuffix": "por noche",
       "compositionTitle": "Stage composition",
       "compositionSubtitle": "Last {nights} nights",
       "compositionAriaLabel": "Sleep stage composition over {nights} nights",

messages/fr.json

@@ -1081,6 +1081,7 @@
       "description": "Stage breakdown and nightly duration, drawn from Apple Health.",
       "headlineTitle": "Average per night",
       "headlineCaption": "Averaged across {count} nights — {suffix}",
+      "headlineCaptionSuffix": "par nuit",
       "compositionTitle": "Stage composition",
       "compositionSubtitle": "Last {nights} nights",
       "compositionAriaLabel": "Sleep stage composition over {nights} nights",

messages/it.json

@@ -1081,6 +1081,7 @@
       "description": "Stage breakdown and nightly duration, drawn from Apple Health.",
       "headlineTitle": "Average per night",
       "headlineCaption": "Averaged across {count} nights — {suffix}",
+      "headlineCaptionSuffix": "per notte",
       "compositionTitle": "Stage composition",
       "compositionSubtitle": "Last {nights} nights",
       "compositionAriaLabel": "Sleep stage composition over {nights} nights",

messages/pl.json

@@ -1081,6 +1081,7 @@
       "description": "Stage breakdown and nightly duration, drawn from Apple Health.",
       "headlineTitle": "Average per night",
       "headlineCaption": "Averaged across {count} nights — {suffix}",
+      "headlineCaptionSuffix": "na noc",
       "compositionTitle": "Stage composition",
       "compositionSubtitle": "Last {nights} nights",
       "compositionAriaLabel": "Sleep stage composition over {nights} nights",

src/components/insights/sleep-overview.tsx

@@ -53,19 +53,13 @@ interface SleepAnalyticsResponse {
 function formatHoursMinutes(
   totalMinutes: number,
   locale: string,
-): { primary: string; suffix: string } {
+): { primary: string } {
   const hours = Math.floor(totalMinutes / 60);
   const mins = Math.round(totalMinutes - hours * 60);
   if (locale === "de") {
-    return {
-      primary: `${hours} Std. ${mins} Min.`,
-      suffix: "pro Nacht",
-    };
+    return { primary: `${hours} Std. ${mins} Min.` };
   }
-  return {
-    primary: `${hours}h ${mins}m`,
-    suffix: "per night",
-  };
+  return { primary: `${hours}h ${mins}m` };
 }
 
 export function SleepOverview() {
@@ -106,10 +100,11 @@ export function SleepOverview() {
   }
 
   const averageMinutes = sleepSummary?.avg30 ?? sleepSummary?.avg7 ?? null;
-  const { primary, suffix } =
+  const suffix = t("insights.sleep.headlineCaptionSuffix");
+  const { primary } =
     averageMinutes != null
       ? formatHoursMinutes(averageMinutes, locale)
-      : { primary: "—", suffix: "" };
+      : { primary: "—" };
 
   return (
     <div className="space-y-4">