♻️ Simplify environment configuration (#2413)

.env

@@ -6,10 +6,8 @@ DOMAIN=localhost
 # DOMAIN=localhost.tiangolo.com
 
 # Public frontend URL, used by the backend to generate links in emails.
-# Keep the Vite URL for local development; deployments use the application URL.
+# Deployments derive this from DOMAIN in compose.deploy.yml.
 FRONTEND_HOST=http://localhost:5173
-# In staging and production, set this env var to the frontend host, e.g.
-# FRONTEND_HOST=https://example.com
 
 # Environment: local, staging, production
 ENVIRONMENT=local
@@ -17,7 +15,8 @@ ENVIRONMENT=local
 PROJECT_NAME="Full Stack FastAPI Project"
 
 # Backend
-BACKEND_CORS_ORIGINS="http://localhost,https://localhost,http://localhost.tiangolo.com"
+# Additional allowed CORS origins, separated by commas
+BACKEND_CORS_ORIGINS=
 SECRET_KEY=changethis
 FIRST_SUPERUSER=admin@example.com
 FIRST_SUPERUSER_PASSWORD=changethis
@@ -39,6 +38,3 @@ POSTGRES_USER=postgres
 POSTGRES_PASSWORD=changethis
 
 SENTRY_DSN=
-
-# Configure these with your own Docker registry images
-DOCKER_IMAGE_BACKEND=backend