Adds Authelia (forward-auth) and nginx portal container for single-endpoint
authenticated access via Caddy reverse proxy. Configures Grafana auth proxy
for header-based auto-login. Updates Vue UI base paths and API routes for
/exabgp/ and /traffic/ subpath serving. Adds traffic-gen responder container
on dedicated Docker network.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
