Replace hardcoded evosync.ru with a DOMAIN variable read from .env.
nginx.conf is now generated from nginx.conf.template via envsubst;
init-letsencrypt.sh reads DOMAIN from .env and fails loudly if unset.
README documents the new variable and first-deploy TLS workflow.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
