Add cancellation and conversion error/success flows

Introduces new components for cancellation and conversion error/success states, updates routing and UI to support resuming and cancelling orders, and refactors seat selection and order handling logic to accommodate these new flows. Also improves seat selection feedback and error handling throughout the checkout process.

src/app/app-routing-module.ts

@@ -27,7 +27,8 @@ const routes: Routes = [
         canActivate: [AuthGuard],
         data: { roles: ['admin'] }, // Array von erlaubten Rollen. Derzeit gäbe es 'admin' und 'employee'
       },
-      { path: 'performance/:performanceId/checkout', component: TheaterOverlayComponent},
+      { path: 'checkout/performance/:performanceId', component: TheaterOverlayComponent},
+      { path: 'checkout/order/:orderId', component: TheaterOverlayComponent},
     ],
   },