feat(deploy): remove cluster allocation section from app creation

Drop the admin-only "cluster assignment" UI from the resources &
config step of the deploy wizard and the related backend override.
App placement is now always decided automatically by the allocator.

- frontend: remove cluster/pool selection block, review-step cluster
  row, clusterMode state, public cluster/pool queries, and clusterId/
  poolId from CreateApplicationDto
- backend: drop clusterId/poolId override from the create DTO and
  simplify ApplicationsService.create to always auto-allocate; widen
  selectClusterForApplication param to keep the fallback path working

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/src/applications/applications.controller.ts

@@ -63,7 +63,7 @@ export class ApplicationsController {
   @Post()
   @ApiOperation({ summary: 'Create a new application' })
   async create(@Request() req: any, @Body() dto: CreateApplicationDto) {
-    return this.applicationsService.create(req.user.id, dto, req.user.role);
+    return this.applicationsService.create(req.user.id, dto);
   }
 
   @Post(':id/upload')