Add Polaris FastAPI backend: models/schemas, pricing+scoring+order router, importer, Celery tasks, API routers, seed script

backend/app/engines/inventory.py

@@ -0,0 +1,72 @@
+"""Inventory sync engine.
+
+Refreshes supplier_products inventory from each adapter, writes inventory_history,
+and flags zero/unavailable stock (pauses published products + audit log alert).
+"""
+from datetime import datetime, timezone
+
+from app.engines.suppliers.base import build_adapter
+from app.models import AuditLog, InventoryHistory, Supplier, SupplierProduct
+
+
+def sync_inventory(db, supplier=None):
+    if supplier is not None:
+        suppliers = [supplier]
+    else:
+        suppliers = db.query(Supplier).filter(Supplier.status == "active").all()
+
+    stats = {"suppliers": len(suppliers), "checked": 0, "changed": 0, "zeroed": 0}
+
+    for s in suppliers:
+        try:
+            adapter = build_adapter(s)
+            current = {r["supplier_sku"]: int(r["inventory"]) for r in adapter.get_inventory()}
+        except Exception as exc:  # noqa: BLE001 — log and continue to next supplier
+            db.add(
+                AuditLog(
+                    actor="inventory",
+                    action="sync_failed",
+                    entity="supplier",
+                    entity_id=str(s.id),
+                    detail={"supplier": s.name, "error": str(exc)},
+                )
+            )
+            continue
+
+        for sp in db.query(SupplierProduct).filter(SupplierProduct.supplier_id == s.id).all():
+            stats["checked"] += 1
+            new_value = current.get(sp.supplier_sku)
+            if new_value is None:
+                continue
+
+            if sp.supplier_inventory != new_value:
+                stats["changed"] += 1
+                sp.supplier_inventory = new_value
+                sp.last_updated = datetime.now(timezone.utc)
+                db.add(InventoryHistory(supplier_product_id=sp.id, inventory=new_value))
+
+            if new_value <= 0:
+                stats["zeroed"] += 1
+                db.add(
+                    AuditLog(
+                        actor="inventory",
+                        action="inventory_zero",
+                        entity="supplier_product",
+                        entity_id=str(sp.id),
+                        detail={"supplier_sku": sp.supplier_sku, "inventory": 0},
+                    )
+                )
+                if sp.product is not None and sp.product.status == "published":
+                    sp.product.status = "paused"
+                    db.add(
+                        AuditLog(
+                            actor="inventory",
+                            action="product_paused_zero_inventory",
+                            entity="product",
+                            entity_id=str(sp.product.id),
+                            detail={"sku": sp.product.sku},
+                        )
+                    )
+
+    db.commit()
+    return stats