Changelog 1.15

• Added configurable save interval (settings.save-interval-ticks) with async autosave plus immediate-write option for safer or faster deployments.
• Reworked DatabaseManager to reuse prepared statements, queue/batch writes, and flush pending updates atomically for lower I/O overhead.
• Transfers now execute in true JDBC transactions; user-facing commands and Vault hook gained new DATABASE_ERROR handling for clearer feedback.
• Plugin lifecycle updates: config reload now refreshes DB scheduling, and shutdown flushes pending writes before closing the connection.