i18n: translate duplicate-timestamp and sleep description in fr/es/it/pl

`measurements.duplicateTimestamp` (the v1.4.28 row-edit banner) and
`insights.sleep.description` (the schlaf sub-page header) both
shipped with English copy in the four non-DE/EN bundles. Replace
with native sentences so a French, Spanish, Italian, or Polish user
sees their own locale on the surfaces this release touched.

messages/es.json

@@ -318,7 +318,7 @@
     "notesPlaceholder": "e.g. after a meal",
     "formReset": "Reset form",
     "saveError": "Error saving",
-    "duplicateTimestamp": "A measurement of this type already exists at the selected timestamp.",
+    "duplicateTimestamp": "Ya existe una medición de este tipo en la marca de tiempo seleccionada.",
     "deleteError": "Error deleting",
     "invalidValue": "Please enter a valid value.",
     "invalidTimestamp": "Please select a valid time.",
@@ -1115,7 +1115,7 @@
     },
     "sleep": {
       "title": "Sueño",
-      "description": "Stage breakdown and nightly duration, drawn from Apple Health.",
+      "description": "Desglose por fases y duración nocturna, tomados de Apple Health.",
       "headlineTitle": "Average per night",
       "headlineCaption": "Averaged across {count} nights — {suffix}",
       "headlineCaptionSuffix": "por noche",

messages/fr.json

@@ -318,7 +318,7 @@
     "notesPlaceholder": "e.g. after a meal",
     "formReset": "Reset form",
     "saveError": "Error saving",
-    "duplicateTimestamp": "A measurement of this type already exists at the selected timestamp.",
+    "duplicateTimestamp": "Une mesure de ce type existe déjà à cet horodatage.",
     "deleteError": "Error deleting",
     "invalidValue": "Please enter a valid value.",
     "invalidTimestamp": "Please select a valid time.",
@@ -1115,7 +1115,7 @@
     },
     "sleep": {
       "title": "Sommeil",
-      "description": "Stage breakdown and nightly duration, drawn from Apple Health.",
+      "description": "Répartition des phases et durée nocturne, issues d’Apple Health.",
       "headlineTitle": "Average per night",
       "headlineCaption": "Averaged across {count} nights — {suffix}",
       "headlineCaptionSuffix": "par nuit",

messages/it.json

@@ -318,7 +318,7 @@
     "notesPlaceholder": "e.g. after a meal",
     "formReset": "Reset form",
     "saveError": "Error saving",
-    "duplicateTimestamp": "A measurement of this type already exists at the selected timestamp.",
+    "duplicateTimestamp": "Esiste già una misurazione di questo tipo a questa marca temporale.",
     "deleteError": "Error deleting",
     "invalidValue": "Please enter a valid value.",
     "invalidTimestamp": "Please select a valid time.",
@@ -1115,7 +1115,7 @@
     },
     "sleep": {
       "title": "Sonno",
-      "description": "Stage breakdown and nightly duration, drawn from Apple Health.",
+      "description": "Suddivisione per fasi e durata notturna, da Apple Health.",
       "headlineTitle": "Average per night",
       "headlineCaption": "Averaged across {count} nights — {suffix}",
       "headlineCaptionSuffix": "per notte",

messages/pl.json

@@ -318,7 +318,7 @@
     "notesPlaceholder": "e.g. after a meal",
     "formReset": "Reset form",
     "saveError": "Error saving",
-    "duplicateTimestamp": "A measurement of this type already exists at the selected timestamp.",
+    "duplicateTimestamp": "Pomiar tego typu już istnieje dla wybranej daty.",
     "deleteError": "Error deleting",
     "invalidValue": "Please enter a valid value.",
     "invalidTimestamp": "Please select a valid time.",
@@ -1115,7 +1115,7 @@
     },
     "sleep": {
       "title": "Sen",
-      "description": "Stage breakdown and nightly duration, drawn from Apple Health.",
+      "description": "Podział na fazy i nocna długość snu, dane z Apple Health.",
       "headlineTitle": "Average per night",
       "headlineCaption": "Averaged across {count} nights — {suffix}",
       "headlineCaptionSuffix": "na noc",