feat: cluster scale command

[Davidonium]

Add cluster scale command

Adds a new qcloud cluster scale command that lets users resize a cluster's compute resources and node count in place.

• Accepts --cpu, --ram, --gpu, --disk, and --nodes flags to adjust any combination of resources in a single operation
• Resolves the appropriate package from the available catalog when resource flags change; skips the catalog lookup entirely when only node count or disk is adjusted
• Computes additional disk storage as the delta between requested total disk and the package's included disk, and rejects disk downscales
• Shows a confirmation prompt with a before/after diff of all changing fields; accepts --force to skip it
• Optionally waits for the cluster to return to a healthy state with --wait, --wait-timeout, and --wait-poll-interval
• Supports shell completion for all resource flags

Also fixes cluster update to use util.ExactArgs for consistent error messages, and cleans up bytes.go to use strings.CutSuffix.