[Aikido] Fix path traversal bypass in normalized filepath comparison logic

[aikido-autofix]

This patch addresses a path traversal vulnerability in the path traversal scanner where attackers could bypass detection by providing exact dangerous directory paths. The vulnerability existed because the scanner was comparing raw user input against dangerous directory prefixes instead of comparing normalized filepaths. The fix normalizes both the resolved filepath and user input before comparison, ensuring consistent path validation. Changes were made to lib/aikido/zen/scanners/path_traversal/helpers.rb and corresponding test cases in test/aikido/zen/scanners/path_traversal_scanner_test.rb to properly detect path traversal attempts.

✅ 1 issue fixed by this PR

Issue	Severity	Description
CodeAudit#811805687	HIGH	PathTraversal::Helpers.start_with_unsafe_path? returns false when the raw payload equals a configured dangerous directory, without requiring the final normalized filepath to equal that directory. For a payload of /etc and a constructed filepath of /etc/passwd, the filepath is recognized as being beneath the dangerous prefix but line 74 takes the exact-prefix exemption. An application endpoint that combines this request-controlled directory with a trusted filename can therefore access a sensitive descendant despite the firewall's blocking mode. The one-character early return for / is a separate residual bypass and should be tracked independently rather than treated as necessary to establish this finding.