fix: eager-load EndpointRow.current_revision_row in get_deployment_data

The DBSource's ``get_deployment_data`` was still selectinload-ing
``EndpointRow.revisions`` while the projection method
``to_model_deployment_data`` reads ``current_revision_row`` /
``deploying_revision_row`` directly. Those relationships default to
``lazy="select"``, so accessing them on a row fetched under an async
session would trip the SQLAlchemy ``greenlet_spawn`` error on every API
path that calls ``get_deployment_data`` (``create_deployment``,
``update_deployment``, ``get_deployment_by_id``, ``activate_revision``).

Align the eager-load with what ``admin_search_deployments`` /
``search_user_deployments`` / ``search_project_deployments`` already do,
and drop the now-unused ``revisions`` chain.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: jopemachine

src/ai/backend/manager/repositories/deployment/db_source/db_source.py

@@ -417,9 +417,8 @@ async def get_deployment_data(
                 sa.select(EndpointRow)
                 .where(EndpointRow.id == endpoint_id)
                 .options(
-                    selectinload(EndpointRow.revisions).selectinload(
-                        DeploymentRevisionRow.image_row
-                    ),
+                    selectinload(EndpointRow.current_revision_row),
+                    selectinload(EndpointRow.deploying_revision_row),
                     selectinload(EndpointRow.deployment_policy),
                 )
             )