Add per-cluster Tools Management and stop auto-installing side tools.

Introduce a catalog-driven Tools Management section under Clusters so
admins can install/uninstall infrastructure tools per cluster: cert-manager
(Helm/jetstack), ClusterIssuer (email + HTTP01 form, depends on cert-manager),
and central Elasticsearch. Cluster creation no longer auto-installs Elastic
or the cloudhost-node-cluster-dns DaemonSet; build bootstrap stays automatic.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend/src/clusters/dto/install-tool.dto.ts

@@ -0,0 +1,14 @@
+import { IsOptional, IsString, IsEmail } from 'class-validator';
+import { ApiPropertyOptional } from '@nestjs/swagger';
+
+export class InstallToolDto {
+  @ApiPropertyOptional({ description: 'ACME email (required for ClusterIssuer)' })
+  @IsOptional()
+  @IsEmail()
+  email?: string;
+
+  @ApiPropertyOptional({ description: 'Ingress class for HTTP01 solver', default: 'nginx' })
+  @IsOptional()
+  @IsString()
+  ingressClass?: string;
+}