feat(contracts): implement staff cancellation of contracts with reason and notification

apps/edr-freight-web/backoffice/src/services/contracts.service.ts

@@ -288,6 +288,13 @@ export const contractsService = {
   reject: (id: string, reason: string) =>
     postContract<Freight.IContract>(C.STAFF_REJECT(id), { reason }),
 
+  /**
+   * Cancel a contract outright. Terminal — unlike {@link suspend} there is no
+   * way back; a new contract with the same details must be submitted instead.
+   */
+  cancelByStaff: (id: string, reason: string) =>
+    postContract<Freight.IContract>(C.STAFF_CANCEL(id), { reason }),
+
   /** Freeze a signed contract. Reversible — see {@link resume}. */
   suspend: (id: string, reason: string) =>
     postContract<Freight.IContract>(C.SUSPEND(id), { reason }),