fix(import): label the SIE preview IB total as "summa debet", not "IB Summa" (#2142)

The fourth stat card in the SIE preview showed the debit-side total of the
opening-balance voucher under the label "IB Summa". A user read it as the
net ingående balans and could not reconcile it against any single figure.

- Relabel the card "IB, summa debet" and add a one-line helper saying it is
  the sum of all debit balances in IB, not a single account balance. The
  number equals "Total debet" in the Balansräkning (IB) card right below.
- Review step: "Skapar IB-verifikation, summa debet X" instead of
  "Skapar verifikation för IB på X".
- Comment the field in generateImportPreview so the meaning is explicit.

No data or logic change: openingBalanceTotal keeps its semantics.


Claude-Session: https://claude.ai/code/session_01AvaV9n4GswzF2Mq932PXTJ

Co-authored-by: Jakob Wennberg <311770904+jakobwennberg-oss@users.noreply.github.com>
Co-authored-by: Claude Fable 5.1 <noreply@anthropic.com>

lib/import/sie-import.ts

@@ -89,6 +89,8 @@ export function generateImportPreview(
     accountCount: parsed.stats.totalAccounts,
     voucherCount: parsed.stats.totalVouchers,
     transactionLineCount: parsed.stats.totalTransactionLines,
+    // Debit-side total of the IB voucher (shown as "IB, summa debet"), not a
+    // net opening balance: a balanced IB nets to zero.
     openingBalanceTotal: totalDebit,
     trialBalance: {
       totalDebit,