M8-T05: bind electricity costs to source bindings

frontend/src/api/schema.d.ts

@@ -1477,6 +1477,11 @@ export interface components {
              * @description FK to the contract version used for this billing period (null when degraded).
              */
             contract_version_id?: number | null;
+            /**
+             * Source Binding Id
+             * @description FK to the source binding that supplied both cumulative endpoints (null for legacy or degraded periods).
+             */
+            source_binding_id?: number | null;
         };
         /**
          * CostsResponse