fix(supplier-invoices): reverse credit notes on paid kontantmetoden invoices (#1430)

Under kontantmetoden the credit flow skipped the reversing verifikat
entirely, gated on accounting_method === 'accrual' in all three surfaces
(dashboard route, v1 route, pending-operations commit).

That is right only while the original is still UNPAID: nothing reached the
ledger, so there is no entry to reverse and recognition waits for cash. But
a PAID original was already booked by its payment verifikat (expense +
2641 ingaende moms). Crediting it marked the invoice 'credited' with zero
accounting trace, leaving both the cost and the moms deduction overstated
and nothing to link a later refund back to.

Adds supplierCreditNoteNeedsJournalEntry(), the mirror of the customer
side's creditNoteNeedsJournalEntry(): reverse whenever the original
actually reached the ledger, whatever the configured method.
createSupplierCreditNoteEntry's existing shape already suits the cash case,
the 2440 debit leaves a claim on the supplier that the refund clears, just
as the customer side leaves a 1510 credit for a refund owed.

The v1 route's GDPR-minimised projection dropped exactly the booked-ness
columns this needs; they are restored with a comment explaining why, since
status alone misses a part-paid-but-booked original (rows predating #1413).

Co-authored-by: Jakob Wennberg <311770904+jakobwennberg-oss@users.noreply.github.com>
Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

lib/pending-operations/commit.ts

@@ -35,7 +35,7 @@ import {
   createCreditNoteJournalEntry,
 } from '@/lib/bookkeeping/invoice-entries'
 import { resolveSettlementAccount } from '@/lib/bookkeeping/settlement-account'
-import { cashPartialBlockReason } from '@/lib/bookkeeping/booking-mode'
+import { cashPartialBlockReason, supplierCreditNoteNeedsJournalEntry } from '@/lib/bookkeeping/booking-mode'
 import { ensureManualCashAccount } from '@/lib/cash-accounts/service'
 import { createJournalEntry, findFiscalPeriod, getSwedishLocalDate, reverseEntry, validateBalance } from '@/lib/bookkeeping/engine'
 import {
@@ -3787,7 +3787,10 @@ async function commitCreditSupplierInvoice(
   const accountingMethod = settings?.accounting_method || 'accrual'
 
   let journalEntryId: string | null = null
-  if (accountingMethod === 'accrual') {
+  // Kontantmetoden skips only while the original is still UNPAID: a paid one
+  // was already booked by its payment verifikat (expense + 2641 ingående
+  // moms), and leaving that un-reversed overstates cost and moms deduction.
+  if (supplierCreditNoteNeedsJournalEntry(accountingMethod, original)) {
     try {
       const je = await createSupplierCreditNoteEntry(
         supabase,