Add conversation image replacement

docs/api.md

@@ -82,6 +82,8 @@ an administrator credential.
 | `POST` | `/api/conversations/{id}/send-reply` | Send a conversation reply | admin | yes |
 | `GET` | `/api/conversations/{id}/shareable-media` | List every enabled exchange-library image not yet shared in this conversation | read | no |
 | `POST` | `/api/conversations/{id}/share-media` | Send a selected exchange-library image | admin | yes |
+| `GET` | `/api/conversations/{id}/image-replacement-options` | List green-screen sources and conversation-owned replacement targets | read | no |
+| `POST` | `/api/conversations/{id}/generate-image-replacement` | Composite a selected conversation image into a green-screen source | admin | yes |
 | `POST` | `/api/conversations/start` | Start a new conversation | admin | yes |
 | `POST` | `/api/conversations/{id}/read` | Advance the operator read watermark | admin | yes |
 | `POST` | `/api/conversations/{id}/unread` | Return a conversation to the unread queue | admin | yes |