Adds Traefik Helm release (kube-system) with ACME HTTP-01 challenge
configured for Let's Encrypt, replacing the k3s-disabled bundled Traefik.
Migrates all hostnames from *.homelab.local to *.gugagr.xyz and upgrades
all ingresses to HTTPS with certresolver=letsencrypt annotations.
Adds var.domain (default homelab.local) to Terraform so the domain is
a single config point for monitoring and Gitea ingresses.
Gateway reads DOMAIN env var at runtime — falls back to homelab.local
so local k3d dev continues to work without changes.
Co-authored-by: Gonçalo Rodrigues <guga@Goncalos-MacBook-Pro.local>
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>