refactor: convert auth and profile commands to structured framework

[Ramon Nogueira (ramon-langchain)]

Summary

• Convert auth login and all profile subcommands to the structured command framework
• Add structured command alias support for profile ls
• Allow structured tables to render a single object for profile show while preserving object-shaped JSON

Test Plan

• go test ./internal/cmd -run 'Test(Auth|Profile)'
• go test ./internal/structured
• deslop internal/structured/command.go internal/structured/specs.go internal/structured/structured_test.go internal/cmd/login.go internal/cmd/profile.go internal/cmd/workspace.go

Note: go test ./... still fails in existing TestTraceMessages_FeedbackStats because it emits "No traces found." where JSON is expected.