Update routing and UI for performance checkout

Changed route paths and parameters for performance checkout to use '/performance/:performanceId/checkout' instead of '/selection/performance/:id'. Updated related components to use new route and param names. Improved UI spacing and styling in several components for better layout and consistency.

src/app/app-routing-module.ts

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