Only ingest online orders for accounts running a POS kitchen

Guard ingestExternalOrder: skip (200, no ticket created) when the owner has no
restaurant-mode POS location, so pushing from Merchant is harmless for accounts
that don't use the POS kitchen.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/Http/Controllers/Api/KitchenIngestController.php

@@ -39,6 +39,11 @@ class KitchenIngestController extends Controller
             return response()->json(['message' => $e->getMessage()], 422);
         }
 
+        // Owner doesn't run a POS kitchen — accept and ignore.
+        if ($sale === null) {
+            return response()->json(['skipped' => true], 200);
+        }
+
         return response()->json(['id' => $sale->id, 'reference' => $sale->reference], 201);
     }