1.6.0 #9: auto-backup programado a iCloud Drive/Archivos

El BackupService (export JSON v3 lossless a local + iCloud ubiquity, retención,
restore, premium-gated) ya existía de 1.1.0 pero solo era manual. Añadido lo automático:
- BackupService.runScheduledBackupIfNeeded() (config vía UserDefaults, gate por
  backupsEnabled+premium, respeta frecuencia).
- Disparo en foreground (scenePhase .active) en background queue.
- Frecuencia Off/Diario/Semanal/Mensual + fecha del último backup en Settings
  (SettingsViewModel.autoBackupFrequencyDays + updateAutoBackupFrequency).
- Strings en 7 idiomas.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01L2p3gUZRNWW388rWFRjiU7

PortfolioJournal/Resources/it.lproj/Localizable.strings

@@ -620,3 +620,11 @@
 "gaps_autofill_cta" = "Riempi %d mesi";
 "Add manually" = "Aggiungi manualmente";
 "Auto-fill estimates the missing months between two snapshots (marked as estimated). Or add the real values yourself." = "Il riempimento automatico stima i mesi mancanti tra due snapshot (contrassegnati come stimati). Oppure inserisci tu i valori reali.";
+
+/* 1.6.0 auto-backup */
+"Auto Backup" = "Backup automatico";
+"Off" = "Disattivato";
+"Daily" = "Giornaliero";
+"Weekly" = "Settimanale";
+"Monthly" = "Mensile";
+"Last auto backup" = "Ultimo backup automatico";