🏢 B2B tax invoices for enterprise license contracts

Context

Enterprise/university licenses are purchased sales-led: a platform admin records the contract payment via recordLicensePayment (src/actions/license.ts), which creates a MANUAL-provider Payment + PLATFORM ADJUSTMENT ledger entry and flips the OrgLicense DRAFT → ACTIVE.

Gap: no Invoice is generated for B2B contracts, even though:

• Invoice/InvoiceSeries models exist (prisma/models/commerce.prisma) with partial unique indexes
• Tenant.gstin is captured on the org tenant but never used
• Retail checkout already writes TAX_INVOICE JSON snapshots (src/lib/commerce/fulfillment.ts)
• Indian GST rules require a tax invoice for B2B supplies; enterprises will demand GST invoices with their own GSTIN as bill-to before paying contracts

Proposed implementation

1. Bill-to resolution — invoice data JSON gains an org bill-to block: legal entity name, billing address, GSTIN (from Tenant), PO/reference number (add OrgLicense.poNumber String? if approved — additive).
2. Series — reuse the existing row-locked InvoiceSeries counter; decide whether B2B contract invoices share series CN/default or get their own series (recommend shared TAX_INVOICE numbering per GST practice — one sequential series).
3. Action — extend recordLicensePayment to create the Invoice in the same transaction as the Payment + ledger entry; amount = contractValueMinor, GST split per configured rate or reverse-charge flag for B2B (input credit model — line items show base + IGST 18% unless tenant config overrides).
4. PDF + email — coordinate with issue #24 (compliance pack): once PDF generation lands, contract invoices render through the same pipeline; until then the numbered DB row + /org license page display is acceptable internally.
5. Placeholders gate — seller entity details come from src/lib/brand.ts placeholders (#37); must be filled before real contracts are invoiced.

Acceptance

• Recording a license payment produces a numbered TAX_INVOICE carrying buyer GSTIN + PO ref
• Invoice appears on /org licenses page and /admin queues
• No schema restructuring — additive only (schema freeze, #43)

Advances #24, #38. Part of epic #42.

Start with recordLicensePayment in src/actions/license.ts, then inspect Invoice and InvoiceSeries in prisma/models/commerce.prisma and the TAX_INVOICE snapshot flow in src/lib/commerce/fulfillment.ts. Review the related constraints from issues #24, #37, #42 and #43 before resolving the series, GST, and PO-number decisions. Done means a transactional, numbered TAX_INVOICE appears with buyer GSTIN and PO reference on the organization licenses page and admin queues.