fix: replace hardcoded French strings in notes-tabs-view with i18n

- Empty notebook placeholder: "Carnet vide" → t('notes.emptyNotebook')
- No note selected: "Aucune note sélectionnée" → t('notes.noNoteSelected')
- Descriptions replaced with t('notes.emptyNotebookDesc'), t('notes.selectOrCreateNote')
- Removed French fallback on newNote button title
- Added 4 new i18n keys to all 15 locales

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

memento-note/locales/es.json

@@ -970,7 +970,11 @@
     "exportPDF": "Exportar PDF",
     "savedStatus": "Guardado",
     "dirtyStatus": "Modificado",
-    "completedLabel": "Completados"
+    "completedLabel": "Completados",
+    "notes.emptyNotebook": "Cuaderno vacío",
+    "notes.emptyNotebookDesc": "Este cuaderno no tiene notas. Haz clic en + para crear una.",
+    "notes.noNoteSelected": "Ninguna nota seleccionada",
+    "notes.selectOrCreateNote": "Selecciona una nota de la lista o crea una nueva."
   },
   "pagination": {
     "next": "→",