XTransfer

Added

• Transactional file migration using a temporary staging directory to ensure all-or-nothing data transfer
• Non-blocking retry mechanism using ScheduledExecutorService with configurable delay between attempts
• Automatic rollback of backup files when the final atomic move operation fails
• Staging directory cleanup on transfer failure to prevent leftover temporary files
• FilePair helper class to encapsulate source, temporary destination, final destination, and critical/optional flag for each migrated file

Fixed

• Thread pool blocking caused by recursive copyWithRetry consuming worker threads during retry waits
• Data inconsistency when some files succeed and others fail during a single transfer operation (partial transfer no longer possible)
• Backup file not being created before the main data copy, risking loss of the target player's original data

Changed

• copyWithRetry now uses ScheduledExecutorService for delayed retries instead of recursive calls on the main executor pool
• copyFile now performs a single copy attempt and returns immediately, with retry logic handled externally
• transferPlayerData and related methods replaced by transferAllFiles, copyAllToTemp, and moveTempToTarget to support transactional migration
• Backup creation and optional file transfers (stats, advancements) integrated into the unified transactional pipeline
• ExecutorService renamed to executor for clarity; new scheduler field added for delayed retry scheduling

Removed

• Recursive retry logic (copyWithRetry calling itself with thenCompose) that blocked worker threads
• Separate backupIfNeeded, transferMainData, transferExtraData, and transferFile methods, consolidated into transferAllFiles and supporting methods
• Direct file overwrite approach that allowed partial transfer states