[Aikido] Fix security issue in immutable

[aikido-autofix]

Upgrade immutable to fix Prototype Pollution vulnerability in merge and conversion APIs that could enable arbitrary code execution.

✅ Code not affected by breaking changes.

No breaking changes affect this codebase. The only breaking change in the changelog relates to TypeScript version requirements (> 4.5), but this is a JavaScript-only project with no TypeScript dependencies. The immutable.js APIs used in the codebase (fromJS(), update(), map(), filter(), get(), List(), toJS(), count()) are stable core methods that remain unchanged in this upgrade.

All breaking changes by upgrading immutable from version 4.0.0-rc.12 to 4.3.8 (CHANGELOG)

Version	Description
4.2.0	Tests are now run with TypeScript > 4.5 only (previously tested with TS > 2.1), which may break implementations using older TypeScript versions

✅ 1 CVE resolved by this upgrade

This PR will resolve the following CVEs:

Issue	Severity	Description
CVE-2026-29063	HIGH	[immutable] Prototype Pollution vulnerability in mergeDeep(), mergeDeepWith(), merge(), Map.toJS(), and Map.toObject() APIs allows attackers to modify object prototypes and potentially execute arbitrary code or bypass security controls.