fix: Reorganize test structure and resolve permission issues

[manavgup]

• Move tests/ from backend/ to project root for better organization
• Fix PermissionError: [Errno 13] Permission denied: '/logs' during testing
• Update Makefile with new test targets and improved volume mounting
• Add support for specific test execution: make test testfile=path/to/test.py
• Add support for specific test function execution: make test testfile=path/to/test.py::test_name
• Update conftest.py to avoid import-time side effects
• Fix log directory creation in main.py to handle testing environment
• Consolidate test structure and remove redundant directories
• Ensure proper environment variables for test isolation

Resolves: #108