docs: add Redis ACL configuration guide for production deployments

[saniddhyaDubey]

Description

Added docs/redis.md documenting the Redis commands used by Nostream and how to configure Redis ACL for production use.

Related Issue

#89

Motivation and Context

Nostream users setting up a restricted Redis user had no documentation on which commands to whitelist in their ACL config.

How Has This Been Tested?

Manually tested the ACL setup locally using Docker Compose — verified all 7 commands work with the restricted nostream user and the default user is disabled.

Screenshots (if appropriate):

All 7 required Redis commands working with restricted nostream user. ACL and WHOAMI correctly blocked:

Default user blocked with NOAUTH error confirming ACL is enforced:

Types of changes

• Non-functional change (docs, style, minor refactor)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my code changes.
• All new and existing tests passed.