fix: gate Permissions import behind #[cfg(unix)] for Windows build

Move `use std::fs::Permissions` and `use std::os::unix::fs::PermissionsExt`
inside the #[cfg(unix)] block to avoid unused import error on Windows.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/windmill-common/src/worker.rs

@@ -1045,16 +1045,17 @@ pub async fn extract_tar(tar: bytes::Bytes, folder: &str) -> error::Result<()> {
 }
 #[cfg(all(feature = "enterprise", feature = "parquet"))]
 fn write_binary_file(main_path: &str, byts: &mut bytes::Bytes) -> error::Result<()> {
-    use std::fs::{File, Permissions};
+    use std::fs::File;
     use std::io::Write;
 
-    #[cfg(unix)]
-    use std::os::unix::fs::PermissionsExt;
-
     let mut file = File::create(main_path)?;
     file.write_all(byts)?;
     #[cfg(unix)]
-    file.set_permissions(Permissions::from_mode(0o755))?;
+    {
+        use std::fs::Permissions;
+        use std::os::unix::fs::PermissionsExt;
+        file.set_permissions(Permissions::from_mode(0o755))?;
+    }
     file.flush()?;
     Ok(())
 }