feat(invoices): registrera utan att bokföra + explicit Bokför-steg (#1040)

* feat(invoices): registrera utan att bokföra + explicit Bokför-steg

Companies where one person registers supplier invoices / sends customer
invoices while ekonomi does the actual bookkeeping had no way to split
the two: under faktureringsmetoden every registration/send booked the
journal entry inline.

- New company setting defer_invoice_booking (default off, accrual only):
  registering a supplier invoice or sending/marking-sent a customer
  invoice creates NO journal entry.
- New explicit booking routes POST /api/supplier-invoices/[id]/book and
  POST /api/invoices/[id]/book: create the registration/revenue entry
  afterwards, CAS-guarded against concurrent booking (a lost race
  cancels the just-posted voucher with a gap explanation), including
  periodisering schedules.
- Detail pages show "Ej bokförd ännu" + a Bokför button for unbooked
  accrual invoices; the settings toggle lives under Bokföringsmetod.
- mark-paid needs no changes: both payment flows already route on the
  journal-entry link, so an invoice still unbooked when paid gets the
  full cash-style entry.
- The mark-sent fail-closed rollback now keys on the same gate so
  deferred sends are not rolled back as booking failures.

Fixes #967

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* fix(invoices): harden deferred booking after review

CodeRabbit round on #1040:
- CAS link guards also require a still-bookable status (and uncredited,
  customer side) so a concurrent mark-paid/credit cannot end up with a
  double-posting registration/revenue entry.
- Settings reads fail closed instead of defaulting to accrual rules.
- Detail pages surface the ACCRUAL_SCHEDULE_FAILED warning instead of
  showing plain success, and the customer page no longer stringifies
  structured errors into "[object Object]".
- The settings form normalizes defer_invoice_booking to false under
  kontantmetoden so a stale flag cannot re-activate on method switch.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

---------

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

components/settings/sections/BookkeepingSettingsContent.tsx

@@ -42,12 +42,18 @@ export function BookkeepingSettingsContent() {
     const lockedThrough = (formData.get('bookkeeping_locked_through') as string) || null
     const accountingMethod = (formData.get('accounting_method') as string) || 'accrual'
     const defaultVoucherSeries = (formData.get('default_voucher_series') as string) || 'A'
+    // Deferred booking is an accrual-only concept (#967): normalize to false
+    // under kontantmetoden so switching back to accrual can never re-activate
+    // a stale flag the user set in a mode where it had no effect.
+    const deferInvoiceBooking =
+      accountingMethod === 'accrual' && formData.get('defer_invoice_booking') === 'true'
 
     const updates: Record<string, unknown> = {
       bookkeeping_locked_through: lockedThrough,
       auto_lock_period_days: autoLockValue === 'none' ? null : parseInt(autoLockValue),
       accounting_method: accountingMethod,
       default_voucher_series: defaultVoucherSeries,
+      defer_invoice_booking: deferInvoiceBooking,
     }
 
     // Write-through: the booking engine resolves the series from the
@@ -110,6 +116,23 @@ export function BookkeepingSettingsContent() {
               {t('method_help')}
             </p>
           </div>
+          {/* #967: register/send without booking; ekonomi books in a separate
+              explicit step. Only meaningful under faktureringsmetoden. */}
+          <div className="space-y-2">
+            <Label htmlFor="defer_invoice_booking">{t('defer_booking_label')}</Label>
+            <select
+              id="defer_invoice_booking"
+              name="defer_invoice_booking"
+              defaultValue={settings.defer_invoice_booking ? 'true' : 'false'}
+              className="flex h-10 w-full max-w-xs rounded-md border border-input bg-background px-3 py-2 text-sm ring-offset-background focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2"
+            >
+              <option value="false">{t('defer_booking_off')}</option>
+              <option value="true">{t('defer_booking_on')}</option>
+            </select>
+            <p className="text-xs text-muted-foreground">
+              {t('defer_booking_help')}
+            </p>
+          </div>
         </section>
 
         {/* Default voucher series */}