Refactor code structure for improved readability and maintainability

backend/.env.example

@@ -4,31 +4,19 @@ APP_VERSION=1.0.0
 DEBUG=True
 ENVIRONMENT=development
 
-# Database - Core (Shared)
+# Database - Core
 CORE_DB_HOST=localhost
 CORE_DB_PORT=5432
 CORE_DB_NAME=anexo76_core
 CORE_DB_USER=postgres
 CORE_DB_PASSWORD=postgres
 
-# Keycloak
-KEYCLOAK_SERVER_URL=http://localhost:8080/kcauth
-KEYCLOAK_REALM=master
-KEYCLOAK_CLIENT_ID=anexo76-backend
-KEYCLOAK_CLIENT_SECRET=your-client-secret
-
-# Security
-SECRET_KEY=your-secret-key-change-in-production
-ALGORITHM=HS256
-ACCESS_TOKEN_EXPIRE_MINUTES=30
-
 # CORS
 CORS_ORIGINS=http://localhost:5173,http://localhost:3000
 
-# License Service
-LICENSE_CHECK_ENABLED=True
+# Hub de Aduanasoft — requerido siempre (SaaS y self-hosted)
+HUB_URL=https://hub.aduanasoft.com
 
-# Synchronization (Hub & Spoke)
+# Sincronización (Hub & Spoke)
 SYNC_SECRET_TOKEN=change-this-sync-token-in-production
-# Only for spokes/clients. Leave empty if this is the Hub.
-CENTRAL_SERVER_URL=http://localhost:8000/api/v1/core/help-center/sync/
+CENTRAL_SERVER_URL=