feat: Add multi-threaded file transfers and enhanced logging support

- Implement concurrent file transfer processing with configurable concurrency
- Add new `max_concurrent_transfers` column to transfer configurations
- Enhance scheduler to support multi-threaded file transfers
- Introduce advanced logging system with rotation and configurable log levels
- Update Docker Compose and documentation with new logging configuration options
- Modify directory structure to separate data, backups, and logs
- Add environment variables for comprehensive logging control
- Improve error handling and logging in file transfer processes

go.mod

@@ -44,6 +44,7 @@ require (
 	golang.org/x/sys v0.30.0 // indirect
 	golang.org/x/text v0.22.0 // indirect
 	google.golang.org/protobuf v1.36.5 // indirect
+	gopkg.in/natefinch/lumberjack.v2 v2.2.1 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 	modernc.org/libc v1.22.5 // indirect
 	modernc.org/mathutil v1.5.0 // indirect