fix: resolve ruff lint issues in storage tool and tests

- Move _ALLOWED_LOG_PREFIXES to module level (N806: constant naming)
- Use f-string conversion flag {e!s} instead of {str(e)} (RUF010)
- Fix import block sorting in both files (I001)

tests/test_storage.py

@@ -8,6 +8,7 @@ from conftest import make_tool_fn
 from unraid_mcp.core.exceptions import ToolError
 from unraid_mcp.tools.storage import format_bytes
 
+
 # --- Unit tests for helpers ---