Add GET /api/documents/inbound/capability (document provider order + vendor-blind
egress class), repoint the vault capability hook to it, and show a per-egress
notice in the detail sheet before a document read leaves the machine. Cover the
document provider order, the egress consent gate, and the notice with tests.
i18n x6 + OpenAPI regenerated.
Co-Authored-By: Marc-André Bombeck