feat: enhance backend security and configuration

- Updated Dockerfile to improve security with a non-root user and added health checks.
- Modified docker-compose.yml to set containers as read-only, restrict ports to localhost, and implement health checks.
- Enhanced .env.example with additional environment variables for security and configuration.
- Improved FastAPI application with middleware for security headers, CORS, and body size limits.
- Refactored authentication flow in auth.py to include state validation and improved error handling.
- Added rate limiting to various endpoints to prevent abuse.
- Updated researcher and publication handling to ensure better validation and error management.

backend/app/services/zip_generator.py

@@ -7,12 +7,16 @@ from xml.etree.ElementTree import Element, SubElement, tostring
 from app.db.models import Publication, Researcher
 from app.services.sword_generator import SWORDGenerator
 
+# ---------------------------------------------------------
+# Clase de generador de ZIP
+# ---------------------------------------------------------
 
 class ZIPGenerator:
 
     # ---------------------------------------------------------
-    # MANIFEST.TXT — más completo
+    # Función auxiliar: generar manifest.txt
     # ---------------------------------------------------------
+
     @staticmethod
     def generate_manifest(researcher, publications):
         lines = [