fix(transactions): resolve bank account from cash_account_id in bulk-book and direct-book dialogs (#770)

Follow-up to #769: applies the same fetch-on-open + resolveAccount pattern to
BulkBookDialog (manual tab bank-leg pre-fill) and BookDirectlyDialog (settlement
line in buildPrefillLines). Both dialogs now fetch /api/cash-accounts when they
open, gate the pre-fill on the fetch resolving, and resolve the correct BAS
ledger account per transaction instead of always emitting '1930'.

Adds lib/cash-accounts/resolve-account.ts (cherry of the utility from #769)
since that PR is not yet merged into main.

Signed-off-by: Jonas Flodén <jonas@floden.nu>

components/transactions/BulkBookDialog.tsx

@@ -4,6 +4,8 @@ import { useEffect, useMemo, useState } from 'react'
 import { useTranslations } from 'next-intl'
 import { createClient } from '@/lib/supabase/client'
 import { useCompany } from '@/contexts/CompanyContext'
+import { resolveAccount } from '@/lib/cash-accounts/resolve-account'
+import type { CashAccount } from '@/types'
 import {
   Dialog,
   DialogContent,
@@ -81,6 +83,8 @@ export default function BulkBookDialog({
   const [templates, setTemplates] = useState<BookingTemplateLibrary[]>([])
   const [loadingTemplates, setLoadingTemplates] = useState(true)
   const [selectedTemplateId, setSelectedTemplateId] = useState<string | null>(null)
+  // null = fetch pending; array = loaded (may be empty on error — falls back to '1930')
+  const [cashAccounts, setCashAccounts] = useState<CashAccount[] | null>(null)
   const [mode, setMode] = useState<Mode>('one_line_per_tx')
   const [description, setDescription] = useState('')
   const [manualLines, setManualLines] = useState<ManualLine[]>([])
@@ -137,6 +141,28 @@ export default function BulkBookDialog({
     }
   }, [open, company, supabase])
 
+  // Fetch cash accounts once when the dialog opens so the manual bank-leg
+  // pre-fill can resolve the correct ledger account per transaction.
+  useEffect(() => {
+    if (!open) return
+    setCashAccounts(null)
+    let cancelled = false
+    fetch('/api/cash-accounts')
+      .then((r) => {
+        if (!r.ok) throw new Error(`cash-accounts fetch failed: ${r.status}`)
+        return r.json()
+      })
+      .then((json) => {
+        if (cancelled) return
+        setCashAccounts((json.data ?? []) as CashAccount[])
+      })
+      .catch(() => {
+        // Fall back to empty list — resolveAccount will return '1930'
+        if (!cancelled) setCashAccounts([])
+      })
+    return () => { cancelled = true }
+  }, [open])
+
   // Reset state when dialog closes so the next open starts clean.
   useEffect(() => {
     if (!open) {
@@ -145,31 +171,43 @@ export default function BulkBookDialog({
       setMode('one_line_per_tx')
       setDescription('')
       setManualLines([])
+      setCashAccounts(null)
     } else if (sharedDate) {
       // Pre-fill description with a sensible default the user can edit.
       setDescription(t('default_description', { date: sharedDate }))
     }
   }, [open, sharedDate, t])
 
-  // Pre-fill the bank side from the txs (one line per tx on 1930 with
-  // the correct Dr/Cr direction). We intentionally do NOT pre-fill a
-  // counterpart account: swedish-compliance flagged that a hardcoded
-  // 3001/5800 prefill nudges users into submitting verifikat without a
-  // VAT line (26xx) for momsregistrerade affärshändelser. The bank
-  // side is the unambiguous part the user always wants; the
+  // Pre-fill the bank side from the txs (one line per tx with the resolved
+  // ledger account and correct Dr/Cr direction). We intentionally do NOT
+  // pre-fill a counterpart account: swedish-compliance flagged that a
+  // hardcoded 3001/5800 prefill nudges users into submitting verifikat
+  // without a VAT line (26xx) for momsregistrerade affärshändelser. The
+  // bank side is the unambiguous part the user always wants; the
   // counterpart (and any VAT split) is the user's responsibility.
+  // Gate on cashAccounts !== null so lines are only built after the account
+  // fetch resolves — this prevents the form from briefly showing '1930' when
+  // the resolved account differs.
   useEffect(() => {
     if (tab !== 'manual') return
     if (manualLines.length > 0) return
     if (transactions.length === 0) return
+    if (cashAccounts === null) return
     const isIncome = direction === 'income'
-    const bankLines: ManualLine[] = transactions.map((tx) => ({
-      id: newManualLineId(),
-      account_number: '1930',
-      debit_amount: isIncome ? Math.abs(tx.amount).toFixed(2).replace('.', ',') : '',
-      credit_amount: isIncome ? '' : Math.abs(tx.amount).toFixed(2).replace('.', ','),
-      line_description: (tx.description || '').slice(0, 40).trim(),
-    }))
+    const bankLines: ManualLine[] = transactions.map((tx) => {
+      const { account } = resolveAccount(
+        cashAccounts,
+        tx.cash_account_id ?? null,
+        tx.currency ?? 'SEK',
+      )
+      return {
+        id: newManualLineId(),
+        account_number: account,
+        debit_amount: isIncome ? Math.abs(tx.amount).toFixed(2).replace('.', ',') : '',
+        credit_amount: isIncome ? '' : Math.abs(tx.amount).toFixed(2).replace('.', ','),
+        line_description: (tx.description || '').slice(0, 40).trim(),
+      }
+    })
     // One empty counterpart row to scaffold the next entry. Account
     // left blank — user must choose, which avoids the no-VAT trap.
     const counterpart: ManualLine = {
@@ -180,7 +218,7 @@ export default function BulkBookDialog({
       line_description: '',
     }
     setManualLines([...bankLines, counterpart])
-  }, [tab, manualLines.length, transactions, direction])
+  }, [tab, manualLines.length, transactions, direction, cashAccounts])
 
   // Live line preview — driven by either the template/mode pair (template
   // tab) or the user-edited manual lines (manual tab). Same downstream