CNFT1-3685: Idle timeout logout modal

[joeaxcdw]

Description

• Replace old dialog with a modal per the Figma design.
• Refactor adding/removing event handlers so they only fire once after component mounted.
• Clean up existing timeout logic - add a debounce to avoid spamming setTimeout calls on every mouse move.
• Show configured timeout value in minutes (no longer hardcoded to 2).
• Add unit tests.

Tickets

• Jira Ticket

Checklist before requesting a review

• PR focuses on a single story
• Code has been fully tested to meet acceptance criteria
• PR is reasonably small and reviewable (Generally less than 10 files and 500 changed lines)
• All new functions/classes/components reasonably small
• Functions/classes/components focused on one responsibility
• Code easy to understand and modify (clarity over concise/clever)
• PRs containing TypeScript follow the Do's and Don'ts
• PR does not contain hardcoded values (Uses constants)
• All code is covered by unit or feature tests