Read project model cards from the virtual scope chain instead of model_cards.project

Replace the ownership predicate in `ProjectModelCardOperationScope` (`src/ai/backend/manager/models/model_card/scopes.py:50`) so the rows it bounds are read from the virtual scope chain instead of the legacy ownership column.

## Current

`ModelCardRow.project == :project_id`

## Target

Resolve membership through `entity_memberships` joined to `virtual_scopes`, keyed on the parent scope's virtual scope node.

Helpers live in `src/ai/backend/manager/models/virtual_scope/queries.py`.

## Write side

Present. src/ai/backend/manager/models/model_card/creators.py:59 declares member_of() -> (ProjectID,).

## Entry points

- `api/gql/model_card/resolver.py:99`
- `api/adapters/model_card/adapter.py:219`

## Done when

- The scope's `to_condition()` no longer references the legacy ownership column.
- A test proves the converted read returns the same rows as the column-based query on backfilled data.

JIRA Issue: BA-7530

Start with ProjectModelCardOperationScope in src/ai/backend/manager/models/model_card/scopes.py and compare its helpers with src/ai/backend/manager/models/virtual_scope/queries.py. Read the write-side declaration in src/ai/backend/manager/models/model_card/creators.py, then inspect the listed resolver and adapter entry points. Add a test showing the converted read returns the same rows as the legacy column query on backfilled data, and confirm to_condition() no longer references that column.

Written by the indexing model from the issue text.