fix(files): batch folder deletion fails

Add debug logging to diagnose batch trash failures for folders.
When batch trash operations fail, the specific error was not being
logged, making it difficult to diagnose issues like #124.

- Add tracing::debug! logs for failed file and folder trash operations
  in batch_operations.rs
- Add unit tests for batch operation result handling to verify
  correct success/failure counting

Fixes #124

src/application/services/mod.rs

@@ -22,6 +22,8 @@ pub mod trash_service;
 pub mod wopi_lock_service;
 pub mod wopi_token_service;
 
+#[cfg(test)]
+mod batch_operations_test;
 #[cfg(test)]
 mod idor_protection_test;
 #[cfg(test)]