Fix/build (#1041)

* fix(bookkeeping): harden correction account changes

* feat(tax): enhance tax deadline generation with new settings and filing methods

- Added new company settings: tax_turnover_over_40m, vat_has_eu_trade, vat_filing_method, periodisk_sammanstallning_enabled, and periodisk_sammanstallning_filing_method.
- Updated deadline generation logic to accommodate new settings affecting VAT and employer declaration deadlines.
- Implemented tests for new functionality, ensuring that completed obligations are preserved and not replaced by new pending rows.
- Introduced a cron job to backfill missing tax deadlines for companies with settings but no upcoming deadlines.
- Updated API routes for generating tax deadlines and handling cron jobs.
- Modified database schema to include new columns for tax filing profiles and constraints for filing methods.

* fix(invoices): record credit note reconciliation guard

* fix(tax): correct automatic deadline settings

* fix(tax): key AGI deadline to VAT taxable base and add storforetag payment deadline

The 26th filing day for the skattedeklaration (AGI and VAT together) hinges
on one statutory measure, a VAT taxable base above SEK 40 million (SFL 26
kap.), not a separate employer turnover. Drop employer_turnover_over_40m and
derive the AGI schedule from vat_registered plus vat_taxable_base_over_40m,
so a non-VAT-reporting employer is never shown the 26th when its binding
date is the 12th.

Also:
- add a skatteinbetalning deadline row (12th, 17 January) for storforetag,
  whose deducted tax and employer contributions are due before the 26th
  filing date
- normalize legally incoherent over-40m flag combinations to the earlier
  small-company schedule in a follow-up migration
- replace hardcoded 27 December dates with the banking-day adjustment
- extend the 40m help text to cover the SKV-decided early filing election
  and the payment-still-on-the-12th rule
- document the regeneration race repaired by the daily backfill cron

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

* feat(migrations): add AGI and VAT filing logic with employer column removal

* feat(settings): implement VAT registration logic and update related flags; enhance deadline handling

---------

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

components/settings/sections/TaxSettingsContent.tsx

@@ -47,19 +47,39 @@ export function TaxSettingsContent() {
 
   function handleSave(formData: FormData) {
     const vatRegistered = formData.get('vat_registered') === 'true'
+    const paysSalaries = formData.get('pays_salaries') === 'true'
 
     const updates: Record<string, unknown> = {
       f_skatt: formData.get('f_skatt') === 'true',
       vat_registered: vatRegistered,
       vat_number: vatRegistered ? ((formData.get('vat_number') as string) || null) : null,
       moms_period: vatRegistered ? ((formData.get('moms_period') as string) || null) : null,
+      vat_taxable_base_over_40m:
+        vatRegistered && formData.get('vat_taxable_base_over_40m') === 'true',
+      vat_has_eu_trade: vatRegistered && formData.get('vat_has_eu_trade') === 'true',
+      // The filing-method and PS selects are conditionally rendered: when a
+      // control is unmounted its FormData key is absent, and defaulting would
+      // silently overwrite the saved preference. Fall back to the stored
+      // value first, then the default.
+      vat_filing_method:
+        (formData.get('vat_filing_method') as string) ||
+        settings?.vat_filing_method ||
+        'electronic',
+      periodisk_sammanstallning_enabled:
+        vatRegistered && formData.get('periodisk_sammanstallning_enabled') === 'true',
       periodisk_sammanstallning_period:
-        (formData.get('periodisk_sammanstallning_period') as string) || 'monthly',
+        (formData.get('periodisk_sammanstallning_period') as string) ||
+        settings?.periodisk_sammanstallning_period ||
+        'monthly',
+      periodisk_sammanstallning_filing_method:
+        (formData.get('periodisk_sammanstallning_filing_method') as string) ||
+        settings?.periodisk_sammanstallning_filing_method ||
+        'electronic',
       tax_contact_name: (formData.get('tax_contact_name') as string) || null,
       tax_contact_phone: (formData.get('tax_contact_phone') as string) || null,
       tax_contact_email: (formData.get('tax_contact_email') as string) || null,
       fiscal_year_start_month: parseInt(formData.get('fiscal_year_start_month') as string) || 1,
-      pays_salaries: formData.get('pays_salaries') === 'true',
+      pays_salaries: paysSalaries,
       preliminary_tax_monthly: parseFloat(formData.get('preliminary_tax_monthly') as string) || null,
     }
     return {