Backend: Add authenticated endpoints for pending association CRUD
(GET/POST/DELETE /api/email-ingestion/pending). Service methods for
resolving (creates fuel/maintenance record) and dismissing associations.
Frontend: New email-ingestion feature with types, API client, hooks,
PendingAssociationBanner (dashboard), PendingAssociationList, and
ResolveAssociationDialog. Mobile-first responsive with 44px touch
targets and full-screen dialogs on small screens.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
