Post-hardening E1: wizard state service, shared UI components, feature tests

[fmenesesg]

Summary

Wave E (final post-hardening wave): Extract migration wizard orchestration into a state service, populate shared/ui/ with reusable components, and expand frontend unit tests.

Scope

• MigrationWizardStateService — wizard state + API orchestration (component-level provider)
• migration-wizard.helpers.ts — pure functions for product filter, prerequisites, validation
• shared/ui/ — LoadingSkeletonComponent, StatusBadgeComponent, BusyOverlayComponent
• Slim MigrationWizardComponent shell binding to the service
• Unit tests for helpers, state service, shared UI, updated wizard specs

Acceptance criteria

• Wizard behavior unchanged (products, analyze, review prerequisites)
• npm test passes (44+ tests)
• shared/README.md documents new components