fix: fix the remote path in SSH when local is Windows (#472)

Fix #471.

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit



- **Improvements**
- Enhanced file path handling for better cross-platform compatibility in
the upload process.
- Improved robustness of temporary file path generation for SHA256
checks and file listings.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Signed-off-by: Jinzhe Zeng <jinzhe.zeng@rutgers.edu>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: njzjz

dpdispatcher/contexts/ssh_context.py

@@ -636,9 +636,9 @@ def upload(
                 ).as_posix()
                 sha256_list.append(f"{sha256}  {jj_rel}")
             # write to remote
-            sha256_file = os.path.join(
-                self.remote_root, ".tmp.sha256." + str(uuid.uuid4())
-            )
+            sha256_file = pathlib.PurePath(
+                os.path.join(self.remote_root, ".tmp.sha256." + str(uuid.uuid4()))
+            ).as_posix()
             self.write_file(sha256_file, "\n".join(sha256_list))
             # check sha256
             # `:` means pass: https://stackoverflow.com/a/2421592/9567349