feat: implement backup system with compression and bundling

- Add zstd-jni dependency for compression support
- Define Backup record with name, key, incremental, and size fields
- Implement BackupManager with backup listing, deletion, and creation methods
- Create BackupWorker to handle backup operations with server state coordination
- Refactor WorldDir to simplify dimension handling and file listing
- Introduce bundling system with SerialBundlerReader^[[1;5P/Writer for efficient storage
- Add BackupStrategy interface with LocalBackupStrategy implementation
- Support both compressed and uncompressed backup formats
- Add config option for parallel backup operations
- Remove old backup implementation from JustBackupMod
- Update backup file format with metadata footer and magic number validation

src/main/java/io/ib67/sfcraft/Backup.java

@@ -0,0 +1,9 @@
+package io.ib67.sfcraft;
+
+public record Backup(
+        String name,
+        String backupKey,
+        boolean incremental,
+        long sizeTotal
+) {
+}