Add Enterprise Stripe invoicing

[Gajesh2007]

Summary

• Add admin-gated Enterprise postpaid billing with cadence, editable Net terms, credit limits, reservations, accrual, rounding carry, and invoice state.
• Wire Enterprise billing through inference paths so active Enterprise accounts bypass prepaid debit while completed usage accrues postpaid and provider/platform/referral accounting still runs.
• Add Stripe invoice/customer support, invoice webhook handling, admin/user APIs, console billing display, and scripts/admin.sh enterprise helpers including --terms-days.
• Add focused store, billing, API, and console tests for Enterprise setup, reservation/cap behavior, invoice lifecycle, terms validation, and UI/status rendering.

Review hardening

• Fail closed on Enterprise lookup errors and enforce open invoices + accrued + reserved + rounding carry + estimate <= credit_limit.
• Make reservations idempotent by account/amount, cap finalized actuals to reserved amounts, and release exposure exactly once on terminal invoice states.
• Persist local draft invoices before Stripe side effects and include pending invoice items when creating Stripe invoices.
• Preserve omitted admin update fields, reject malformed invoice-run JSON, and keep below-cent accrued usage carried forward.

Validation

• cd coordinator && GOCACHE=/tmp/go-build go test ./internal/store ./internal/billing ./internal/api
• cd coordinator && GOCACHE=/tmp/go-build go test -count=1 ./cmd/coordinator
• cd console-ui && npm test -- billing
• cd console-ui && npx eslint src/ __tests__/billing-enterprise.test.tsx (passes with existing warnings, 0 errors)
• git diff --check

Notes

• Draft PR because this is a broad billing stack change and should get human product/security review before merge.
• Live Postgres integration was not run because DATABASE_URL is not configured in this worktree.

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Project	Deployment	Actions	Updated (UTC)
d-inference	Ready	Preview	Apr 29, 2026 2:26pm
d-inference-console-ui-dev	Ready	Preview	Apr 29, 2026 2:26pm
d-inference-landing	Ready	Preview	Apr 29, 2026 2:26pm