fix: make account usage refresh resilient

[SilkageNet]

Summary

• serialize per-account App Server requests and multi-account refreshes
• retry transient usage failures up to three times while carrying forward rotated credentials
• preserve complete per-account refresh failures in the usage cache and surface them in table/JSON output
• extend the automatic cache freshness window from one to five minutes

Validation

• go test -race ./...
• golangci-lint run
• real account list --refresh against two saved Pro accounts using Codex CLI 0.158.0-alpha.2.1