oss: CLI login + result reporting to platform API

[jeff-atriumn]

Summary

Add noxaudit login and automatic result reporting so CLI users with a SaaS account can sync audit results to the platform dashboard.

noxaudit login

• Opens browser for GitHub OAuth flow (callback to platform API)
• Stores token in ~/.noxaudit/credentials
• noxaudit logout clears the token
• noxaudit whoami shows the logged-in user and org

Result reporting

When logged in, noxaudit run POSTs results to POST /api/audits after the local audit completes. The local workflow is unchanged — reports still write to local files. The platform is an additional destination.

Offline-first

• If the platform API is unreachable, the CLI works normally
• Results queue locally in ~/.noxaudit/pending-sync.jsonl
• Next successful noxaudit run (or explicit noxaudit sync) flushes the queue

Work

• noxaudit login command — browser OAuth flow
• Token storage in ~/.noxaudit/credentials (file permissions 600)
• noxaudit logout and noxaudit whoami commands
• After run_audit completes, POST to platform API if logged in
• Local queue for offline resilience
• noxaudit sync command to manually flush queued results

Depends on

• atriumn/noxaudit-platform#5 (auth — OAuth flow, no billing needed)
• atriumn/noxaudit-platform#20 (audit ingestion API)

Does NOT depend on

• atriumn/noxaudit-platform#24 (Stripe billing) — login and reporting work regardless of payment status