This commit introduces several improvements to the application configuration and logging mechanisms, including:
- Added a new `REDIS_URL` configuration option in the production environment template for easier Redis setup.
- Implemented a soft delete method in the `UserManager` class to anonymize user data while maintaining referential integrity.
- Enhanced session secret management to ensure a secure fallback in non-production environments.
- Introduced a `PiiRedactionFilter` to loggers for redacting sensitive information from logs.
- Added rate limiting middleware to control API request rates and prevent abuse.
These changes aim to improve security, maintainability, and user data protection within the application.
