chore(per-instance-hook-scoping): archive verified+synced change

Move to openspec/changes/archive/2026-07-09-per-instance-hook-scoping/
(R100 renames preserved). 9 artifacts. Canonical openspec/specs/
service-instance-scoping/ remains. Resolves multi-instance wrong-data bug
(hooks now scope by instance.id; instance switcher re-scopes).
Carry-overs: fetchBackupDashboard untouched (design decision 5); subquery
scoping for runs/alerts (schema asymmetry).

backend/src/media_library_viewer_api/routers/backups.py

@@ -183,7 +183,10 @@ def get_backup_alerts(
     store: SettingsStore = Depends(get_settings_store),
 ) -> list[BackupAlertResponse]:
     alerts = store.list_backup_alerts(
-        job_id=job_id, acknowledged=acknowledged, severity=severity, service_id=service_id,
+        job_id=job_id,
+        acknowledged=acknowledged,
+        severity=severity,
+        service_id=service_id,
     )
     return [BackupAlertResponse(**alert) for alert in alerts]
 

backend/tests/test_backups.py

@@ -76,12 +76,8 @@ class TestBackupServiceScoping:
         job_b = store.upsert_backup_job({"name": "job-b", "service_id": "svc-b"})
         store.create_backup_run({"job_id": job_a["id"], "started_at": 1700000000, "status": "success"})
         store.create_backup_run({"job_id": job_b["id"], "started_at": 1700000000, "status": "success"})
-        store.create_backup_alert(
-            {"job_id": job_a["id"], "alert_type": "test", "severity": "warning"}
-        )
-        store.create_backup_alert(
-            {"job_id": job_b["id"], "alert_type": "test", "severity": "warning"}
-        )
+        store.create_backup_alert({"job_id": job_a["id"], "alert_type": "test", "severity": "warning"})
+        store.create_backup_alert({"job_id": job_b["id"], "alert_type": "test", "severity": "warning"})
         assert len(store.list_backup_alerts(service_id="svc-a")) == 1
         assert len(store.list_backup_alerts(service_id="svc-b")) == 1