Adds the UI surface for the credit system to /orgs:
- CreditsPill next to each org row. Tone shifts from zinc → amber at
10% of plan to red at zero.
- LowCreditsBanner appears under the pill for running orgs when the
balance crosses thresholds: overage_used > 0 → "overage active",
balance <= 0 → "out of credits, upgrade", trial tail → "trial almost
out".
- Pure helpers extracted to lib/credits.ts so formatCredits, pillTone,
and bannerKind are unit-tested without jsdom.
Backend List query now returns credits_balance / plan_monthly_credits
/ overage_used_credits / overage_cap_credits so no second round-trip
is needed.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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