Split e-invoice exports into a separate server-only subpath

@e-invoice-eu/core pulls in Node-only dependencies (tmp/tmp-promise, for
a LibreOffice conversion path this package never actually takes) that
broke Next.js's client bundle the moment renderInvoiceEInvoice() was
re-exported from the main "." entry — that entry is reachable from a
Client Component (email-templates.ts's Live Preview import chain), so
the bundler tried pulling e-invoice-eu/core in client-side too.

New "@einfach-produktiv/invoicing/einvoice" subpath (package.json
"exports" map + src/einvoice/index.ts) holds only the e-invoice
generation functions — server-only code (API routes, Server Components,
Payload job handlers) imports from there instead. The main "." entry
keeps everything already browser-safe (computeTaxBreakdown, formatters,
InvoiceDocument for Live Preview's <PDFViewer>, the plain PDF renderers).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

package.json

@@ -6,6 +6,16 @@
   "type": "module",
   "main": "./src/index.ts",
   "types": "./src/index.ts",
+  "exports": {
+    ".": {
+      "types": "./src/index.ts",
+      "default": "./src/index.ts"
+    },
+    "./einvoice": {
+      "types": "./src/einvoice/index.ts",
+      "default": "./src/einvoice/index.ts"
+    }
+  },
   "scripts": {
     "typecheck": "tsc --noEmit",
     "test": "vitest run",

src/einvoice/index.ts

@@ -0,0 +1,12 @@
+// Server-only entry point (`@einfach-produktiv/invoicing/einvoice`),
+// separate from the package's main "." entry — see that entry's own
+// comment on why: @e-invoice-eu/core pulls in Node-only dependencies that
+// break a client bundle the moment they're reachable from code a Client
+// Component also imports. Only import this from server-only code (API
+// routes, Server Components, Payload job handlers) — never from anything
+// a "use client" file also imports, directly or transitively.
+export { renderInvoiceEInvoice, renderCorrectionInvoiceEInvoice } from "./renderEInvoice";
+export { buildEInvoiceData, buildCorrectionEInvoiceData } from "./buildEInvoiceData";
+export type { InvoiceOrder } from "../invoicePdf";
+export type { CorrectionInvoiceKind, CorrectionInvoiceOrder } from "../correctionInvoicePdf";
+export type { InvoiceSeller } from "../seller";

src/index.ts

@@ -14,5 +14,14 @@ export {
   type CorrectionInvoiceItem,
   type CorrectionInvoiceOrder,
 } from "./correctionInvoicePdf";
-export { renderInvoiceEInvoice, renderCorrectionInvoiceEInvoice } from "./einvoice/renderEInvoice";
-export { buildEInvoiceData, buildCorrectionEInvoiceData } from "./einvoice/buildEInvoiceData";
+
+// E-invoice generation (renderInvoiceEInvoice/renderCorrectionInvoiceEInvoice)
+// is deliberately NOT re-exported from here — @e-invoice-eu/core pulls in
+// Node-only dependencies (tmp/tmp-promise, used for its LibreOffice
+// conversion path, even though this package never takes that path) that
+// broke Next.js's client bundle the moment they got pulled in transitively
+// through this same barrel file (this file is itself imported by
+// email-templates.ts, which a Client Component needs for its Live
+// Preview). Import from "@einfach-produktiv/invoicing/einvoice" instead —
+// a separate subpath, server-only code paths only (see that folder's own
+// index.ts).