fix: loop FileChannel.transferTo() — it can transfer fewer bytes than requested without looping, silently truncating files

src/main/java/com/dostalgia/StaticResource.java

@@ -171,7 +171,15 @@ public class StaticResource {
             } else {
                 // Partial content (Range request) — transfer only the requested bytes
                 try (FileChannel ch = FileChannel.open(file, StandardOpenOption.READ)) {
-                    ch.transferTo(offset, length, java.nio.channels.Channels.newChannel(output));
+                    long remaining = length;
+                    long pos = offset;
+                    while (remaining > 0) {
+                        long written = ch.transferTo(pos, remaining,
+                            java.nio.channels.Channels.newChannel(output));
+                        if (written <= 0) break;
+                        pos += written;
+                        remaining -= written;
+                    }
                 }
             }
         }