feat(salary): öresavrundning of net pay to whole kronor (#1609)

* feat(salary): öresavrundning of net pay to whole kronor

Some banks reject salary payment files whose amounts carry öre. New
company_settings.salary_net_rounding toggle (off by default): the engine
rounds each net payout up to the next whole krona, never down, and emits
a derived oresavrundning line item (semesterersattning pattern) that
debits 3740 Öres- och kronutjämning so the salary entry stays balanced.
Gross, tax and avgifter are untouched, so AGI/KU are unaffected. Payment
files (pain.001 + Bankgirot LB) get whole-krona amounts via the rounded
net_salary. Toggle in salary settings; payslip and run detail show the
line item.

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

* fix(salary): keep employer cost on the shared definition; block manual rounding lines

Skeptic findings on the öresavrundning commit: (1) the engine included
netRounding in totalEmployerCost while payslip summary, KPI cards and
lönejournal recompute the figure from stored columns, printing two
different totals on the same payslip; employer cost now stays on the
shared definition and the öre cost is carried by the 3740 ledger line.
(2) 'oresavrundning' is excluded from the line-item create/update
schemas: it is the only item type the booking keeps out of the gross
reconciliation, so a manually created row would structurally unbalance
the salary verifikat.

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

* fix(salary): add the item_type CHECK as NOT VALID, validate separately

Compliance-swarm finding (SOC 2 CC8.1): the CHECK re-add scanned
salary_line_items under the ADD's ACCESS EXCLUSIVE lock. Split per the
house pattern (DECISIONS.md 2026-07-13): 20260813143000 re-adds the
constraint NOT VALID, new 20260813143001 validates it under SHARE UPDATE
EXCLUSIVE in its own transaction. The list is a strict superset of the
previous CHECK, so validation cannot fail. Both files are branch-only,
so editing in place is within the never-modify-shipped rule.

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

---------

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

components/settings/sections/SalarySettingsContent.tsx

@@ -14,6 +14,7 @@ import {
   SettingsSelect,
 } from '@/components/settings/SettingsRows'
 import { TaxTableStatus } from '@/components/salary/TaxTableStatus'
+import { Switch } from '@/components/ui/switch'
 import { useSettings } from '@/components/settings/useSettings'
 import { resolveDefaultSeriesForSource } from '@/lib/bookkeeping/voucher-series-resolver'
 import type { CompanySettings } from '@/types'
@@ -36,11 +37,15 @@ export function SalarySettingsContent() {
   const { settings, isLoading, updateSettings, refetch } = useSettings()
   // Controlled so the LB sunset note reacts to the selection before save.
   const [format, setFormat] = useState<'bg_lb' | 'pain001' | null>(null)
+  // Controlled: the Radix Switch is not a form element, so its value rides
+  // along in handleSave instead of FormData.
+  const [netRounding, setNetRounding] = useState<boolean | null>(null)
 
   if (isLoading) return <SettingsLoadingSkeleton />
   if (!settings) return <SettingsLoadError onRetry={refetch} />
 
   const effectiveFormat = format ?? settings.preferred_payment_format ?? 'pain001'
+  const effectiveNetRounding = netRounding ?? settings.salary_net_rounding ?? false
   const currentSeries = resolveDefaultSeriesForSource(settings, 'salary_payment')
 
   function handleSave(formData: FormData) {
@@ -54,6 +59,7 @@ export function SalarySettingsContent() {
       salary_pay_day: payDay,
       preferred_payment_format: paymentFormat,
       salary_default_bank: bank === 'none' ? null : bank,
+      salary_net_rounding: effectiveNetRounding,
     }
 
     // The booking engine resolves the series from the per-source-type map;
@@ -132,6 +138,16 @@ export function SalarySettingsContent() {
               <option value="other">{t('bank_other')}</option>
             </SettingsSelect>
           </SettingsRow>
+          <SettingsRow label={t('net_rounding_label')} help={t('net_rounding_help')}>
+            <Switch
+              id="salary_net_rounding"
+              checked={effectiveNetRounding}
+              onCheckedChange={(next) => setNetRounding(next)}
+            />
+            <label htmlFor="salary_net_rounding" className="cursor-pointer text-sm">
+              {t('net_rounding_toggle')}
+            </label>
+          </SettingsRow>
         </SettingsGroup>
 
         <SettingsGroup label={t('accounting_heading')}>