feat: implement region file reassembly and improve bundle format

- Add fastutil and lz4-java dependencies for efficient data structures and compression
- Implement VarInt/VarLong serialization for more compact bundle headers
- Redesign bundle header format to include timestamps and use variable-length integers
- Replace GZIP-based compression with region file reassembly for better compression of chunk data
- Add RegionFile and RegionFileReassembler classes for handling Minecraft region files
- Implement configurable compression types (GZIP, ZLIB, LZ4, NONE) for region files
- Add timestamp filtering and duplicate handling to BundleReader
- Improve parallel processing capabilities with configurable worker threads
- Add JUnit 5 testing support and configure shadowJar minimization
- Update file extensions from .jpack to .jbp.zst for clarity
- Enhance error handling and logging throughout the codebase
- Add comprehensive region file manipulation including chunk-level recompression
- Implement memory-efficient region file parsing using Netty ByteBuf
- Add support for dictionary-based Zstd compression
- Update backup worker to use new bundle format
- Various performance optimizations and bug fixes

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

@@ -40,7 +40,7 @@ public record BackupWorker(
         var backupName = "Backup_" + DateTimeFormatter.ISO_LOCAL_DATE_TIME.format(LocalDateTime.now());
         var backupParentRoot = Path.of(config.temporaryBackupDir());
         if (Files.notExists(backupParentRoot)) Files.createDirectories(backupParentRoot);
-        var backupFile = backupParentRoot.resolve(backupName + ".jpack");
+        var backupFile = backupParentRoot.resolve(backupName + ".jbp.zst");
         try {
             if (i == 0) {
                 // not saved yet.

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

@@ -23,6 +23,7 @@ import net.fabricmc.api.ModInitializer;
 
 import net.fabricmc.fabric.api.command.v2.CommandRegistrationCallback;
 import net.fabricmc.fabric.api.event.lifecycle.v1.ServerLifecycleEvents;
+import net.jpountz.lz4.LZ4BlockInputStream;
 import net.minecraft.command.CommandRegistryAccess;
 import net.minecraft.server.MinecraftServer;
 import net.minecraft.server.command.CommandManager;