Ajoute la suppression complète d'un ticket (#6).
Backend Rust :
- port IssueStore::delete (NotFound si absent) + event IssueDeleted{freed_sprint}
- FsIssueStore::delete : supprime .ideai/tickets/<N>/ et l'index sous lock
- use case DeleteIssue + adaptations des tests sprint/ticket_assistant au port
- commande Tauri ticket_delete + câblage events/state/lib
Frontend :
- gateway delete (ports, adapter ticket + mock, domain)
- useTicketDetail : retrait de la liste et fermeture du détail via event issueDeleted
- intégration TicketDetail + tests
Tests verts : application/issue_usecases (6), infrastructure/issue_store (7),
app-tauri --lib (56), frontend vitest (503), npm run build (exit 0).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>