feat(rust): implement full Redis cluster and RabbitMQ queue_info parsing

- Implement proper RabbitMQ queue_info endpoint with passive queue declare
  - Returns actual message_count and consumer_count from RabbitMQ
  - Returns exists: false when queue doesn't exist (instead of error)

- Implement parsed redis_cluster_nodes endpoint
  - Parses CLUSTER NODES raw output into structured JSON
  - Includes node_id, host, port, role, flags, slots_count, slot_ranges

- Implement parsed redis_cluster_slots endpoint
  - Parses redis::Value::Array into structured slot_distribution
  - Includes master/replica info with host and port
  - Calculates total_slots and coverage_percentage

- Implement parsed redis_cluster_info endpoint
  - Parses CLUSTER INFO key:value pairs into JSON object
  - Converts numeric values to integers

- Implement parsed redis_node_info endpoint
  - Adds node name validation (redis-1, redis-2, redis-3)
  - Parses INFO output into sections (server, clients, memory, etc.)
  - Returns 400 for invalid node names

- Update tests to accept 503 when RabbitMQ is unavailable
  - Aligns with existing Redis cluster test patterns

This brings Rust API to ~100% feature parity with FastAPI baseline
for Redis cluster and RabbitMQ endpoints.

Author: NormB