feat(invoices): expose the automatic reminder kill switch in settings (#1476)

* feat(invoices): expose the automatic reminder kill switch in settings

The send_invoice_reminders column, API schema, and cron processor check
already existed, but no UI ever exposed the toggle. Add a switch in
Settings -> Fakturering (day thresholds fold away when off, values
preserved), and make the invoice detail Paminnelser card say reminders
are off instead of promising emails that will never be sent.

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

* fix(invoices): do not assume reminders enabled before settings load

CodeRabbit finding on PR 1476: with no company_settings row loaded, the
Paminnelser card defaulted to promising the reminder schedule. Track the
toggle as boolean | null and render no schedule text until the settings
row has actually resolved.

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

---------

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

components/settings/sections/InvoicingSettingsContent.tsx

@@ -37,6 +37,7 @@ export function InvoicingSettingsContent() {
         Number.parseInt(formData.get('reminder_days_level_2') as string) || 30,
       reminder_days_level_3:
         Number.parseInt(formData.get('reminder_days_level_3') as string) || 45,
+      send_invoice_reminders: formData.get('send_invoice_reminders') === 'true',
     }
     return {
       updates,