refactor(forte-drop): remove standalone subdomain cert+route

The forteapp chart now supports tls.additionalDomains (multi-SAN) and
ingress.priority (forte-helm#10), so the per-slug wildcard cert and the
low-priority HostRegexp IngressRoute no longer need to be standalone
overlay resources. Routing + cert move to the forte-drop release values
(helm-prod-values). The issuer dnsZones change stays here.

Depends on forte-helm#10 (ingress.priority) merged + synced before the
values flip, else the consolidated HostRegexp would outrank and steal
mcp.drop.forteapps.net.

Refs #22

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/overlays/upc-dev/forte-drop/kustomization.yaml

@@ -5,5 +5,3 @@ resources:
 - keycloak-client-forte-drop.yaml
 - forte-drop-pdb.yaml
 - forte-drop-secrets-sealed.yaml
-- wildcard-drop-tls-certificate.yaml
-- forte-drop-subdomains-ingressroute.yaml