Redis connection: add TLS, auth, Sentinel, and Cluster support

[jerry7991]

Problem

lib/nebula_queue/connection.rb:26:

Redis.new(url: config.redis_url)

Only a URL is supported. Production Redis deployments typically require one or more of:

• TLS (rediss:// + CA bundle / client cert).
• Password / ACL auth (separate from the URL for secret-store injection).
• Redis Sentinel (high availability via sentinels: + name: options).
• Redis Cluster (redis-clustering gem, different client class).
• Read/write timeouts (connect_timeout, read_timeout, write_timeout).

Fix

1. Expose config.redis_options as a hash passed through to Redis.new, merged on top of { url: redis_url }.
2. Document recommended production settings (timeouts, TLS).
3. Add a config.sentinels shortcut and document the Sentinel topology.
4. Consider a config.client_class override for users on Redis Cluster / redis-client.

Acceptance

• config.redis_options = { ssl_params: {...}, password: ENV['REDIS_PASSWORD'], connect_timeout: 2 } works end-to-end.
• README has a "Production Redis" section.