Fix: Temporary file cleanup security vulnerability (#67)

* Fix temporary file cleanup security issue

This commit addresses a critical security vulnerability where temporary files created during multipart form parsing were not properly cleaned up from disk, potentially leading to:
- Information disclosure of sensitive uploaded data
- Disk space exhaustion from accumulated temp files
- File descriptor leaks in error scenarios

Changes:
- Added filePath field to preProcessor struct to track temp file location
- Modified preProcessor.Close() to explicitly remove temp files using os.Remove()
- Ensured both file handle closure and file deletion with proper error handling

The existing defer hsc.Close() in Parse() ensures cleanup even on errors.

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

* remove filepath field

---------

Co-authored-by: Claude <noreply@anthropic.com>

Author: mazrean

parse.go

@@ -219,7 +219,20 @@ func (pp *preProcessor) Close() error {
 		return nil
 	}
 
-	return pp.file.Close()
+	filepath := pp.file.Name()
+
+	// Close the file handle first
+	closeErr := pp.file.Close()
+
+	// Remove the temporary file from disk
+	removeErr := os.Remove(filepath)
+
+	// Return combined errors if any
+	if closeErr != nil || removeErr != nil {
+		return errors.Join(closeErr, removeErr)
+	}
+
+	return nil
 }
 
 type judgeHook struct {