Wire Vite allowed hosts to env for Docker frontend

.env.example

@@ -40,6 +40,7 @@ PROVIDER_BASE_URL_ALLOWLIST=[]
 PUBLIC_BASE_URL=http://localhost:8000
 CORS_ORIGINS=["http://localhost:5173","http://localhost:3000"]
 VITE_API_BASE=
+VITE_ALLOWED_HOSTS=
 
 # Optional frontend build network and npm fetch tuning:
 DOCKER_BUILD_NETWORK=default
@@ -61,3 +62,4 @@ NPM_FETCH_TIMEOUT=300000
 # PUBLIC_BASE_URL=https://api.example.com
 # CORS_ORIGINS=["https://app.example.com"]
 # VITE_API_BASE=https://api.example.com/api/v1
+# VITE_ALLOWED_HOSTS=app.example.com