feat(mileage): surface Körjournal in the nav behind a settings toggle (#1540)

* feat(mileage): surface Körjournal in the nav behind a settings toggle

The /mileage page shipped hidden: the route works but no nav row points at
it. Add company_settings.mileage_enabled (mirroring dimensions_enabled) with
a switch in Fönster -> Bokföring, and show the Arbeta nav row when the toggle
is on OR the company already has mileage_trips rows, the same hybrid gate as
webshop orders, so trips created via API/MCP can never become invisible
underlag. UI visibility only, never load-bearing for correctness.

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

* fix(migrations): move mileage_enabled migration after already-applied 20260812153208

origin/main merged in 20260812153208 which prod has already applied; a new
file sorting before it risks an out-of-order db push abort.

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

---------

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

components/settings/sections/BookkeepingSettingsContent.tsx

@@ -13,6 +13,7 @@ import { VoucherSeriesPerSourceTypeForm } from '@/components/settings/VoucherSer
 import { applyDefaultSeriesToMap } from '@/lib/bookkeeping/voucher-series-resolver'
 import { PeriodiseringAutoDetectToggle } from '@/components/settings/PeriodiseringAutoDetectToggle'
 import { DimensionsToggle } from '@/components/settings/DimensionsToggle'
+import { MileageToggle } from '@/components/settings/MileageToggle'
 import { AccountingFrameworkForm } from '@/components/settings/AccountingFrameworkForm'
 import {
   SettingsGroup,
@@ -174,6 +175,7 @@ export function BookkeepingSettingsContent() {
       <SettingsGroup label={t('group_automation')}>
         <PeriodiseringAutoDetectToggle />
         <DimensionsToggle />
+        <MileageToggle />
       </SettingsGroup>
 
       <SettingsGroup>