fix: scale replicas in response, YAML lineWidth, delta values, modified keys

- Scale API now returns actual replicas in instance response
- ModifyModal: fix YAML stringify line breaking (lineWidth: 0)
- ModifyModal: show modified keys summary above YAML editor
- ModifyModal: only send delta (user-modified) values to server
- Add diffObjects helper for deep object comparison

backend/internal/adapter/input/http/rest/instance_handler.go

@@ -393,8 +393,11 @@ func (h *InstanceHandler) ScaleInstance(w http.ResponseWriter, r *http.Request)
 		return
 	}
 
+	instResp := convertInstanceResponse(result, true)
+	instResp.Replicas = req.Replicas
+
 	respondJSON(w, http.StatusOK, dto.ScaleInstanceResponse{
-		Instance: convertInstanceResponse(result, true),
+		Instance: instResp,
 		Replicas: req.Replicas,
 		Message:  fmt.Sprintf("Scaled to %d replicas", req.Replicas),
 	})