Upgrade to Svelte 4.2.0

[yutenglei]

• Svelte Upgrade: Updated the project to Svelte version 4.2.0.
• Dependency Update: Ran yarn upgrade --latest to ensure all dependencies are up to date.
• ESM Adoption: Transitioned to ESM for svelte-testing-library. This change is prompted by the recent release of testing-library/svelte-testing-library v4.0.0, which introduced ESM support as a breaking change.
• Testing Framework Migration: Migrated from Jest to Vitest, aligning with the recommended testing setup outlined in the Svelte Testing Library documentation.

These updates ensure compatibility, improve maintainability, and align with best practices.