fix(deploy): resolver 502 CMS remoto y estandarizar buildx/s3

- corrige host remoto de deploy y automatiza buildx en servidor
- agrega configuracion S3 (bucket openccb-802726101181-us-east-2-an)
- actualiza Dockerfile de studio a rust:1-bookworm para evitar error GLIBC
- activa cache mounts de buildkit para cargo/npm en studio

.env.example

@@ -56,6 +56,15 @@ MYSQL_DATABASE_URL=mysql://db_user:db_password@host:3306/database_name
 EXTERNAL_TABLE_GRADES=notas
 EXTERNAL_ID_TIPO_NOTA=1
 
+# ----------------------------------------
+# AWS S3 Configuration (audio storage)
+# Bucket: openccb-802726101181-us-east-2-an
+# ----------------------------------------
+AWS_ACCESS_KEY_ID=
+AWS_SECRET_ACCESS_KEY=
+AWS_REGION=us-east-2
+S3_BUCKET=openccb-802726101181-us-east-2-an
+
 # ----------------------------------------
 # Mercado Pago Configuration
 # ----------------------------------------