store: Add restore orchestration in SubgraphStore and DeploymentStore

Wire up the restore pipeline through SubgraphStore::restore() and
DeploymentStore::restore(). Uses plan_restore() to determine whether to
create or replace the deployment site, validates the target shard exists,
resolves the subgraph name for deployment rule matching, and assigns the
restored deployment to a node.

Changes:
- DeploymentStore::restore() coordinates schema creation, data import,
  and finalization
- Inner::restore() handles conflict resolution, site allocation, and
  node assignment via deployment rules
- Expose create_site() and find_active_site() on primary::Connection
- Make create_site() accept an `active` parameter