v1.3

Added

• Folder marker support: PUT with trailing slash (e.g., folder/) creates directories
• DELETE support for folder markers
• Empty directories persist after deleting files inside (S3-like behavior)
• Makefile with test-unit, test-integration-up, test-integration-down, build commands
• Folder marker integration tests

Fixed

• ListObjects prefix filter now correctly matches directories with trailing slashes
• Directories now report size 0 instead of filesystem block size

Improved

• Storage test coverage increased to 80%
• Makefile clears test cache and greps for FAIL to catch errors