feat: implement standard toast notification system (#191)

[Francis6-git]

This PR improves how we show feedback to users through notifications with a single system using react-hot-toast.

Changes Made

• New Hook (src/hooks/use-notification.ts): Created a wrapper hook to provide a consistent API for success, error, and loading states. It handles message formatting (including Error objects and arrays) to ensure the UI never breaks.
• FormWizardController: Integrated toast feedback for step validation failures and final submission success/error states.
• DynamicFormBuilder: Added notifications for configuration parsing errors, auto-save failures, and form submission lifecycle.
• AutoSaveManager: Standardized internal saving status to trigger global toasts on critical failures.

Closes #191

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