fix(transactions): steer duplicate guard to matching for ledger-only vouchers (#958)

When the booking-time duplicate guard flags a ledger-only voucher
candidate (transaction_id null: a verifikat from an SIE import, a paid
invoice, a salary payout), the dialog's primary action is now "Matcha
mot verifikatet": it links the bank transaction to the existing voucher
via /api/reconciliation/bank/link (the same path MatchVoucherDialog
uses) instead of double-booking the same affarshandelse. "Bokfor anda"
stays available but demoted to an outline button. Sibling-transaction
candidates keep today's layout: matching a second bank line onto a
voucher that already has one is the N:1 edge case, not the default.

Wired through both call sites: the transactions page (runCategorize)
reuses handleVoucherLinked's refresh, and TransactionBookingDialog
(JournalEntryForm, /api/transactions/[id]/book path) reuses the booked
flow so in-dialog attached documents land on the matched verifikat and
the row leaves the list, with a "Bankhandelsen kopplad" toast instead
of "Bokford". No lib change: the candidate payload already carries the
transaction_id discriminator, covered by existing detection tests.

Closes #919.

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

lib/transactions/__tests__/booking-duplicate-detection.test.ts

@@ -76,6 +76,7 @@ describe('detectBookedDuplicateTransaction', () => {
       entry_date: '2025-12-19',
       description: 'TELENOR SVERIGE AB',
       amount: -1616,
+      account_number: null,
     })
   })
 
@@ -251,6 +252,9 @@ describe('detectLedgerDuplicateVoucher', () => {
       entry_date: '2026-03-30',
       description: 'Inbetalning kundfaktura 2026001',
       amount: 98565,
+      // The matched leg's account rides along so the dialog's match action
+      // links on the exact 19xx the voucher was booked to (issue #919).
+      account_number: '1930',
     })
   })
 
@@ -270,6 +274,7 @@ describe('detectLedgerDuplicateVoucher', () => {
     expect(result?.journal_entry_id).toBe('je-3')
     expect(result?.transaction_id).toBeNull()
     expect(result?.amount).toBe(16609)
+    expect(result?.account_number).toBe('1930')
   })
 
   it('does NOT flag an inbound receipt against a credit-only voucher (wrong direction)', async () => {

lib/transactions/booking-duplicate-detection.ts

@@ -46,6 +46,14 @@ export interface BookedDuplicateCandidate {
   entry_date: string
   description: string | null
   amount: number
+  /**
+   * The 19xx settlement account of the voucher leg that matched, set for
+   * ledger-only candidates so the match action can link on the exact account
+   * the voucher was booked to (a legacy transaction without cash_account_id
+   * would otherwise resolve by currency and can pick the wrong 19xx). Null for
+   * sibling-transaction candidates, whose legs are not fetched.
+   */
+  account_number: string | null
 }
 
 /** Minimal shape of the transaction about to be booked. */
@@ -162,6 +170,7 @@ export async function detectBookedDuplicateTransaction(
     entry_date: entryDate,
     description: best.description,
     amount: roundOre(Number(best.amount)),
+    account_number: null,
   }
 }
 
@@ -327,6 +336,7 @@ export async function detectLedgerDuplicateVoucher(
     entry_date: best.journal_entry.entry_date,
     description: best.journal_entry.description,
     amount: roundOre(Number(inbound ? best.debit_amount : best.credit_amount)),
+    account_number: best.account_number,
   }
 }