feat: transaction categorization UX improvements and description matching

Add journal entry preview, human-readable account names, auto-apply VAT,
fallback template suggestions, example prompts, invoice match comparison,
and batch result feedback. Also includes user-description-match extension,
describe/batch-describe API routes, improved AI categorization with multi-
suggestion support, and template embedding search.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

components/transactions/JournalEntryPreview.tsx

@@ -0,0 +1,114 @@
+'use client'
+
+import { useMemo } from 'react'
+import { formatCurrency } from '@/lib/utils'
+import { formatAccountWithName } from '@/lib/bookkeeping/client-account-names'
+import { getVatRate, extractVatAmount, extractNetAmount } from '@/lib/bookkeeping/vat-entries'
+import { getCategoryAccountMapping } from '@/lib/bookkeeping/category-mapping'
+import type { TransactionCategory, VatTreatment } from '@/types'
+
+interface PreviewLine {
+  side: 'debet' | 'kredit'
+  account: string
+  amount: number
+}
+
+interface JournalEntryPreviewProps {
+  amount: number
+  currency?: string
+  category?: TransactionCategory
+  vatTreatment?: VatTreatment | 'none'
+  accountOverride?: string
+  /** For template-based bookings — overrides category mapping */
+  templateDebitAccount?: string
+  templateCreditAccount?: string
+  templateVatRate?: number
+}
+
+export default function JournalEntryPreview({
+  amount,
+  currency = 'SEK',
+  category,
+  vatTreatment,
+  accountOverride,
+  templateDebitAccount,
+  templateCreditAccount,
+  templateVatRate,
+}: JournalEntryPreviewProps) {
+  const lines = useMemo(() => {
+    const result: PreviewLine[] = []
+    const absAmount = Math.abs(amount)
+
+    // Template-based preview
+    if (templateDebitAccount && templateCreditAccount) {
+      const vatRate = templateVatRate ?? 0
+      const vatAmt = extractVatAmount(absAmount, vatRate)
+      const netAmt = extractNetAmount(absAmount, vatRate)
+
+      result.push({ side: 'debet', account: templateDebitAccount, amount: netAmt })
+      if (vatAmt > 0) {
+        result.push({ side: 'debet', account: '2641', amount: vatAmt })
+      }
+      result.push({ side: 'kredit', account: templateCreditAccount, amount: absAmount })
+      return result
+    }
+
+    // Category-based preview
+    if (!category) return result
+
+    const resolvedVat = vatTreatment === 'none' ? undefined : vatTreatment
+    const mapping = getCategoryAccountMapping(category, amount, category !== 'private', 'enskild_firma', resolvedVat)
+
+    const debitAccount = accountOverride && amount < 0 ? accountOverride : mapping.debitAccount
+    const creditAccount = accountOverride && amount > 0 ? accountOverride : mapping.creditAccount
+
+    const treatment = mapping.vatTreatment as VatTreatment | null
+    const vatRate = treatment ? getVatRate(treatment) : 0
+    const vatAmt = vatRate > 0 ? extractVatAmount(absAmount, vatRate) : 0
+    const netAmt = vatRate > 0 ? extractNetAmount(absAmount, vatRate) : absAmount
+
+    if (amount < 0) {
+      // Expense: Debit expense + VAT, Credit bank
+      result.push({ side: 'debet', account: debitAccount, amount: netAmt })
+      if (vatAmt > 0 && mapping.vatDebitAccount) {
+        result.push({ side: 'debet', account: mapping.vatDebitAccount, amount: vatAmt })
+      }
+      result.push({ side: 'kredit', account: creditAccount, amount: absAmount })
+    } else {
+      // Income: Debit bank, Credit revenue + VAT
+      result.push({ side: 'debet', account: debitAccount, amount: absAmount })
+      if (vatAmt > 0 && mapping.vatCreditAccount) {
+        result.push({ side: 'kredit', account: mapping.vatCreditAccount, amount: vatAmt })
+      }
+      result.push({ side: 'kredit', account: creditAccount, amount: netAmt })
+    }
+
+    // Reverse charge: add offsetting lines
+    if (treatment === 'reverse_charge' && amount < 0) {
+      const rcVatAmt = Math.round(absAmount * 0.25 * 100) / 100
+      result.push({ side: 'debet', account: '2645', amount: rcVatAmt })
+      result.push({ side: 'kredit', account: '2614', amount: rcVatAmt })
+    }
+
+    return result
+  }, [amount, category, vatTreatment, accountOverride, templateDebitAccount, templateCreditAccount, templateVatRate])
+
+  if (lines.length === 0) return null
+
+  return (
+    <div className="rounded-lg border bg-muted/30 px-3 py-2.5">
+      <p className="text-xs font-medium text-muted-foreground mb-1.5">Verifikation</p>
+      <div className="space-y-0.5 font-mono text-xs">
+        {lines.map((line, i) => (
+          <div key={i} className="flex items-baseline gap-2">
+            <span className={`w-12 text-right flex-shrink-0 ${line.side === 'debet' ? 'text-foreground' : 'text-muted-foreground'}`}>
+              {line.side === 'debet' ? 'Debet' : 'Kredit'}
+            </span>
+            <span className="flex-1 truncate">{formatAccountWithName(line.account)}</span>
+            <span className="flex-shrink-0 tabular-nums">{formatCurrency(line.amount, currency)}</span>
+          </div>
+        ))}
+      </div>
+    </div>
+  )
+}