feat: add cluster logs command

[Davidonium]

Add cluster logs command

Adds a new qcloud cluster logs <cluster-id> subcommand that retrieves log entries for a cluster via the Monitoring gRPC service.

Usage

qcloud cluster logs <cluster-id> [flags]

Flags:
  -s, --since string   Start time for logs (RFC3339 or YYYY-MM-DD, default: 3 days ago)
  -u, --until string   End time for logs (RFC3339 or YYYY-MM-DD, default: now)
  -t, --timestamps     Prepend each log line with its timestamp
      --json           Output as JSON

Details

• Time filters accept both RFC3339 (2024-01-01T00:00:00Z) and date-only (2024-01-01) formats. When omitted, the server applies its own defaults.
• The --timestamps flag prepends each line with a human-readable UTC timestamp; without it only the raw log message is printed.
• --json outputs the full response proto, consistent with other commands.
• Cluster ID shell completion is wired up via the existing completion helper.