feat(azure-ai+gpu-ui): per-tenant Azure AI config + GPU health panel

- Per-tenant Azure AI config stored in tenants.tenant_config JSONB
- GET/PUT /api/tenants/{id}/ai-config + POST .../test connection
- api_key never returned to frontend (has_api_key: bool pattern)
- azure_ai.py resolves creds from tenant config when ai_enabled=True
- ai_tasks.py loads tenant config and passes it to validate_thumbnail
- Admin GPU Status section: probe button + status badge + last-checked time
- Notifications: _BELL_CHANNELS filter (notification+alert only in bell)
- Tenants.tsx: per-row Azure AI Config modal with URL auto-parse helper
- Remove duplicate in-memory /gpu-probe endpoints (kept DB-backed /probe/gpu)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/tasks/ai_tasks.py

@@ -7,11 +7,34 @@ logger = logging.getLogger(__name__)
 
 @celery_app.task(bind=True, name="app.tasks.ai_tasks.validate_item", queue="ai_validation")
 def validate_item(self, order_item_id: str):
-    """Validate orientation of a rendered thumbnail via Azure GPT-4o Vision."""
+    """Validate orientation of a rendered thumbnail via Azure GPT-4o Vision.
+
+    Loads the order item's tenant config and passes it to validate_thumbnail()
+    so that per-tenant Azure credentials are used when configured.
+    """
     logger.info(f"AI validation for item: {order_item_id}")
     try:
+        from app.config import settings
+        from sqlalchemy import create_engine
+        from sqlalchemy.orm import Session
+        from app.models.order_item import OrderItem
         from app.services.azure_ai import validate_thumbnail
-        validate_thumbnail(order_item_id)
+
+        # Load tenant config for this order item
+        tenant_config: dict | None = None
+        try:
+            engine = create_engine(settings.database_url_sync)
+            with Session(engine) as session:
+                item = session.get(OrderItem, __import__("uuid").UUID(order_item_id))
+                if item and hasattr(item, "order") and item.order and item.order.tenant_id:
+                    from app.domains.tenants.models import Tenant
+                    tenant = session.get(Tenant, item.order.tenant_id)
+                    if tenant:
+                        tenant_config = tenant.tenant_config or {}
+        except Exception as exc:
+            logger.warning(f"Could not load tenant config for {order_item_id}: {exc}")
+
+        validate_thumbnail(order_item_id, tenant_config=tenant_config)
     except Exception as exc:
         logger.error(f"AI validation failed for {order_item_id}: {exc}")
         raise self.retry(exc=exc, countdown=30, max_retries=3)