Mount the shared ToastProvider in providers.tsx and replace the inline
error/success banners across the overview, items list, board, item detail
and public roadmap with toast() calls — load errors, create, delete, vote,
status/priority/visibility updates, comment add, and idea submission. The
roadmap submit now toasts + closes the dialog instead of an in-modal
banner; the item-detail page keeps a single inline empty-state for the
hard "couldn't load this item" case.
Generated with [Devin](https://cli.devin.ai/docs)
Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>
3fc559d066