Add /relay* location block to Caddyfile template so that NetBird relay
WebSocket connections (rels://) are correctly forwarded to the relay
container instead of falling through to the dashboard handler.
Without this fix, all relay WebSocket connections silently hit the
dashboard container, causing STUN/relay connectivity failures for all
deployed NetBird instances.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>