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/schema/auth.py

@@ -1,11 +1,17 @@
 from pydantic import BaseModel, Field
 
+# ---------------------------------------------------------
+# Modelo de solicitud de login OAuth
+# ---------------------------------------------------------
 
 class OrcidLoginRequestSchema(BaseModel):
     # `code` is the authorization code returned by ORCID OAuth after the user signs in.
     # Exchanging it for tokens must happen server-side.
     code: str = Field(..., examples=["Q70Y3A"])
 
+# ---------------------------------------------------------
+# Modelo de respuesta de login OAuth
+# ---------------------------------------------------------
 
 class OrcidLoginResponseSchema(BaseModel):
     access_token: str