feat: enhance RedisClusterTemplate for CI and hybrid environments

[joshrotenberg]

Summary

This PR adds features to improve RedisClusterTemplate usability in CI environments and hybrid local/CI setups, addressing issues #207, #208, #209, and #210.

Changes

RedisClusterConnection (#207)

• Add new() constructor for direct node list creation without needing a template
• Add with_password() for authenticated connections
• Add nodes() getter for accessing the node list

Environment Configuration (#208)

• Add from_env() to configure templates via environment variables:
  • REDIS_CLUSTER_PORT_BASE: Base port (default: 7000)
  • REDIS_CLUSTER_NUM_MASTERS: Number of masters (default: 3)
  • REDIS_CLUSTER_NUM_REPLICAS: Replicas per master (default: 0)
  • REDIS_CLUSTER_PASSWORD: Optional password
• Add getter methods: get_port_base(), get_num_masters(), get_num_replicas()

Health Check Helpers (#209)

• Add is_ready() to check if cluster state is "ok"
• Add wait_until_ready(timeout) for polling until cluster is ready
• Add TemplateError::Timeout variant for timeout errors

Hybrid Setup Support (#210)

• Add detect_existing() to find running clusters at configured ports
• Add start_or_detect(timeout) - uses existing cluster if available, otherwise starts new one

Usage Example

// Works in both CI (uses existing cluster) and local (starts new cluster)
let template = RedisClusterTemplate::from_env("test-cluster");
let conn = template.start_or_detect(Duration::from_secs(60)).await?;

println!("Cluster ready at: {}", conn.nodes_string());

Testing

• All 760 unit tests pass
• Added 5 new tests for the new functionality

Closes #207, #208, #209, #210