feat(shared-filesystem-storage): migrate ShareItem to functional TypeScript (#2053)

[hodanoori]

Summary

Migrates ShareItem in the shared filesystem storage plugin from a class component to a functional TypeScript component as part of the React 19 migration epic (#1774).

Changes Made

• Replace class component ShareItem with a functional TypeScript component in item.tsx
• Replace componentDidMount, UNSAFE_componentWillReceiveProps, and componentWillUnmount with useEffect hooks managing polling via useRef
• Convert inner RuleTooltip class component to a functional component
• Convert startPolling and stopPolling to inline effect logic using useRef for the interval ID
• Add TypeScript interfaces for Rule, ShareRulesState, Share, ShareNetwork, and ShareItemProps
• Delete item.jsx
• Add item.test.tsx with 18 unit tests covering row rendering, share network and rules display, dependency loading, and polling lifecycle

Related Issues

• Issue: closes [Task](shares): Migrate shares/item.jsx #2053
• Epic: [EPIC](react-19): Upgrade to React 19 #1774

Screenshots (if applicable)

Checklist

• I have performed a self-review of my code.
• I have commented my code, particularly in hard-to-understand areas.
• I have added tests that prove my fix is effective or that my feature works.
• New and existing unit tests pass locally with my changes.
• I have made corresponding changes to the documentation (if applicable).
• My changes generate no new warnings or errors.