feat: migrate purelb to ArgoCD (#84)

Migrate PureLB load balancer from Terragrunt to ArgoCD/Kustomize.
Deploys purelb v0.13.0 with two LBNodeAgent and two ServiceGroup CRs
(common: 198.18.200.0/24, dmz: 198.18.199.0/24).
Adds LBNodeAgent and ServiceGroup to kubeconform skip list (no CRD catalog schema).

💘 Generated with Crush

Assisted-by: Claude Sonnet 4.6 via Crush <crush@charm.land>

Reviewed-on: #84

ci/validate-apps.sh

@@ -18,6 +18,6 @@ while IFS= read -r -d "" k; do
         -summary \
         -output pretty \
         -verbose \
-        -skip CustomResourceDefinition,GpuDevicePlugin \
+        -skip CustomResourceDefinition,GpuDevicePlugin,LBNodeAgent,ServiceGroup \
         "${schema_args[@]}"
 done < <(find apps/overlays -name kustomization.yaml -print0)