Humanize file sizes in gen output, clean up temp on signal

- Humanize file sizes in verbose file listing (e.g., "76.8 MiB" not "76836984 bytes")
- Add signal handler to clean up temp file on Ctrl-C/SIGTERM during gen

internal/scanner/scanner.go

@@ -10,6 +10,7 @@ import (
 	"sync"
 	"time"
 
+	"github.com/dustin/go-humanize"
 	"github.com/spf13/afero"
 	"sneak.berlin/go/mfer/internal/log"
 	"sneak.berlin/go/mfer/mfer"
@@ -354,7 +355,7 @@ func (s *Scanner) ToManifest(ctx context.Context, w io.Writer, progress chan<- S
 			return err
 		}
 
-		log.Verbosef("+ %s (%d bytes)", entry.Path, bytesRead)
+		log.Verbosef("+ %s (%s)", entry.Path, humanize.IBytes(uint64(bytesRead)))
 
 		scannedFiles++
 		scannedBytes += bytesRead