feat(workflows): hard cutover of gallery-expiry + dunning + pre-event to flows

Seed gallery_expiring / gallery_expired built-ins and make the live automations
flow-owned, with zero feature loss:

- New delegating actions (notify_gallery_expiring / notify_gallery_expired /
  notify_pre_event) call the EXISTING send functions, so the engine path is
  byte-identical to the legacy hourly checker/pass (same templates, recipients,
  variables, dedup, per-event overrides, sent_at idempotency).
- Cutover built-ins (invoice_dunning, gallery_expiring, gallery_expired,
  pre_event_email) now ship ENABLED; booking flows stay disabled (stubs).
- The legacy paths stand down via existence-based isBuiltinFlowPresent guards:
  once a built-in is seeded (flag on) the engine is the single switch — flow
  enabled = it sends, flow disabled = off — so no double-send and reminders/
  expiry emails can still be fully turned off.
- emitDueEventReminders now honours the per-event reminder controls
  (disabled / offset / sent_at) so pre-event timing is faithful; fixed a
  Number(null)===0 offset bug.

Settings UI cutover is gated on the `workflows` flag (default off): when the
engine is live, the dunning reminder schedule (CRM settings) and the pre-event
global toggle (Reminder emails) are replaced with a "now in Workflows" callout;
when it's off, the legacy controls stay so flag-off installs lose nothing. The
late-fee math and installment-trigger defaults stay (fee math / scheduler-owned).

Split/installment invoices intentionally remain scheduler-driven (no flow).

frontend/src/i18n/locales/de.json

@@ -4920,6 +4920,11 @@
       "title": "Mahngebühren müssen in den AGB stehen",
       "body": "Vertragliche Pflicht: Sätze wie „Es werden Mahnspesen erhoben“ reichen nicht aus. In den AGB muss die konkrete Gebühr klar beziffert sein (z.B. „CHF 20 ab der 2. Mahnung“). Mit dem Treuhänder prüfen."
     },
+    "dunningMoved": {
+      "title": "Der Mahnrhythmus liegt jetzt in den Workflows",
+      "body": "Wann und wie oft Zahlungserinnerungen für überfällige Rechnungen verschickt werden, wird im Workflow „Rechnungsmahnung“ festgelegt. Die Mahngebühren unten gelten weiterhin.",
+      "link": "Workflows öffnen"
+    },
     "crm_invoices_late_fee_label": {
       "label": "Bezeichnung Mahngebühr"
     },
@@ -5023,6 +5028,11 @@
   },
   "reminderTemplates": {
     "title": "Erinnerungs-E-Mails vor dem Anlass",
+    "scheduleMoved": {
+      "title": "Der Versandzeitpunkt liegt jetzt in den Workflows",
+      "body": "Ob Erinnerungen vor dem Anlass verschickt werden und wie viele Tage vorher, wird im Workflow „Erinnerung vor dem Anlass“ festgelegt. Auf dieser Seite werden die E-Mail-Vorlagen bearbeitet; anlassspezifische Überschreibungen bleiben auf der jeweiligen Anlass-Detailseite.",
+      "link": "Workflows öffnen"
+    },
     "globalSection": "Globales Verhalten",
     "globalHelp": "Standardmässig aus — aktiviere, um Erinnerungen zu senden. Der unten gesetzte Offset ist der Standard; jeder Anlass kann ihn auf der Detailseite überschreiben.",
     "enableLabel": "Erinnerungs-E-Mails vor dem Anlass senden",

frontend/src/i18n/locales/en.json

@@ -4918,6 +4918,11 @@
       "title": "Late fees must be itemised in your terms (AGB)",
       "body": "A contractual duty: phrases like “late fees apply” aren't enough. Your terms must state the concrete fee (e.g. “CHF 20 from the 2nd reminder”). Verify with your Treuhänder."
     },
+    "dunningMoved": {
+      "title": "Reminder schedule is now in Workflows",
+      "body": "When and how often overdue reminders go out is configured in the “Invoice dunning” workflow. The late-fee amounts below still apply.",
+      "link": "Open Workflows"
+    },
     "crm_invoices_late_fee_label": {
       "label": "Late fee label"
     },
@@ -5021,6 +5026,11 @@
   },
   "reminderTemplates": {
     "title": "Pre-event reminder emails",
+    "scheduleMoved": {
+      "title": "The reminder schedule is now in Workflows",
+      "body": "Whether pre-event reminders are sent, and how many days before the event, is configured in the “Pre-event reminder” workflow. This page edits the email templates; per-event overrides stay on each event’s detail page.",
+      "link": "Open Workflows"
+    },
     "globalSection": "Global behaviour",
     "globalHelp": "Off by default — turn on to start sending pre-event reminders. The offset below is the default; each event can override on its detail page.",
     "enableLabel": "Send pre-event reminder emails",

frontend/src/pages/admin/settings/CrmSettingsPage.tsx

@@ -8,8 +8,9 @@
  */
 import React, { useEffect, useState } from 'react';
 import { useTranslation } from 'react-i18next';
+import { Link } from 'react-router-dom';
 import { useMutation, useQuery, useQueryClient } from '@tanstack/react-query';
-import { Save as SaveIcon } from 'lucide-react';
+import { Save as SaveIcon, Workflow as WorkflowIcon } from 'lucide-react';
 import { Button, Card, Loading, Input } from '../../../components/common';
 import { settingsService } from '../../../services/settings.service';
 import { quotesService } from '../../../services/quotes.service';
@@ -83,6 +84,10 @@ export const CrmSettingsPage: React.FC = () => {
   // invoice-pipeline + revenue tiles, all of which are CRM-money).
   const showQuotes = !!flags.quotes;
   const showInvoices = !!flags.bills;
+  // When the workflow engine is live, reminder TIMING is owned by the Invoice
+  // dunning flow — show a pointer instead of the legacy schedule controls. When
+  // it's off, the legacy reminder ladder still runs, so keep its controls.
+  const workflowsLive = !!flags.workflows;
   const showContracts = !!flags.contracts;
   const showDashboardOverview = !!(flags.quotes || flags.bills);
   const anySection = showQuotes || showInvoices || showContracts || showDashboardOverview;
@@ -244,7 +249,26 @@ export const CrmSettingsPage: React.FC = () => {
       <Card>
         <h3 className="font-semibold mb-3">{t('crmSettings.section.invoices', 'Invoices')}</h3>
         {checkbox('crm_invoices_qr_enabled', 'Render payment QR on invoice PDFs')}
-        {checkbox('crm_invoices_reminders_enabled', 'Send automatic reminders for overdue invoices')}
+
+        {/* Reminder TIMING: owned by the Invoice dunning workflow when the
+            engine is live (callout); otherwise the legacy schedule controls. The
+            late-fee math below is configured here in both cases — it's the fee
+            the dunning path applies, not part of the schedule. */}
+        {workflowsLive ? (
+          <div className="mt-2 rounded-lg border border-blue-300 dark:border-blue-700 bg-blue-50 dark:bg-blue-900/20 p-3 text-sm text-blue-800 dark:text-blue-200 flex items-start gap-2">
+            <WorkflowIcon className="w-4 h-4 mt-0.5 shrink-0" />
+            <div>
+              <p className="font-medium">{t('crmSettings.dunningMoved.title', 'Reminder schedule is now in Workflows')}</p>
+              <p className="mt-1">
+                {t('crmSettings.dunningMoved.body', 'When and how often overdue reminders go out is configured in the “Invoice dunning” workflow. Late-fee amounts below still apply.')}{' '}
+                <Link to="/admin/workflows" className="underline font-medium">{t('crmSettings.dunningMoved.link', 'Open Workflows')}</Link>
+              </p>
+            </div>
+          </div>
+        ) : (
+          checkbox('crm_invoices_reminders_enabled', 'Send automatic reminders for overdue invoices')
+        )}
+
         {checkbox('crm_invoices_late_fee_enabled', 'Add a late fee (Mahngebühr) on the 2nd and 3rd reminder')}
         <div className="mt-2 rounded-lg border border-amber-300 dark:border-amber-700 bg-amber-50 dark:bg-amber-900/20 p-3 text-sm text-amber-800 dark:text-amber-200">
           <p className="font-medium">{t('crmSettings.lateFeeAgb.title', 'Late fees must be itemised in your terms (AGB)')}</p>
@@ -252,14 +276,18 @@ export const CrmSettingsPage: React.FC = () => {
         </div>
         {checkbox('crm_invoices_late_fee_vat_enabled', 'Charge VAT on late fees (Switzerland — leave off for DE/AT; no effect if your organisation has no VAT rate)')}
         <div className="grid grid-cols-1 md:grid-cols-2 gap-3 mt-3">
-          <Input type="number" min={1} max={365}
-            label={t('crmSettings.crm_invoices_reminder_first_days.label', 'First reminder after (days past due)') as string}
-            value={values.crm_invoices_reminder_first_days ?? 14}
-            onChange={(e) => setVal('crm_invoices_reminder_first_days', Number(e.target.value))} />
-          <Input type="number" min={1} max={365}
-            label={t('crmSettings.crm_invoices_reminder_second_days.label', 'Second reminder after (days past due)') as string}
-            value={values.crm_invoices_reminder_second_days ?? 30}
-            onChange={(e) => setVal('crm_invoices_reminder_second_days', Number(e.target.value))} />
+          {!workflowsLive && (
+            <>
+              <Input type="number" min={1} max={365}
+                label={t('crmSettings.crm_invoices_reminder_first_days.label', 'First reminder after (days past due)') as string}
+                value={values.crm_invoices_reminder_first_days ?? 14}
+                onChange={(e) => setVal('crm_invoices_reminder_first_days', Number(e.target.value))} />
+              <Input type="number" min={1} max={365}
+                label={t('crmSettings.crm_invoices_reminder_second_days.label', 'Second reminder after (days past due)') as string}
+                value={values.crm_invoices_reminder_second_days ?? 30}
+                onChange={(e) => setVal('crm_invoices_reminder_second_days', Number(e.target.value))} />
+            </>
+          )}
           <div>
             <label className="block text-sm font-medium text-neutral-700 dark:text-neutral-300 mb-1">
               {t('crmSettings.crm_invoices_late_fee_type.label', 'Late fee type')}

frontend/src/pages/admin/settings/ReminderTemplatesPage.tsx

@@ -33,13 +33,14 @@ import { useTranslation } from 'react-i18next';
 import { Link } from 'react-router-dom';
 import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
 import { toast } from 'react-toastify';
-import { ArrowLeft, Save, AlertTriangle } from 'lucide-react';
+import { ArrowLeft, Save, AlertTriangle, Workflow as WorkflowIcon } from 'lucide-react';
 import { Button, Card, Loading, Input } from '../../../components/common';
 import { SUPPORTED_LANGUAGES } from '../../../components/common/LanguageSelector';
 import { EmailTemplateEditor } from '../../../components/admin/EmailTemplateEditor';
 import { eventTypesService } from '../../../services/eventTypes.service';
 import { emailService, type EmailTemplateTranslation } from '../../../services/email.service';
 import { settingsService } from '../../../services/settings.service';
+import { useFeatureFlags } from '../../../contexts/FeatureFlagsContext';
 
 const TEMPLATE_KEY_DEFAULT = 'event_reminder_default';
 const TEMPLATE_KEY_PREFIX = 'event_reminder_';
@@ -61,16 +62,20 @@ export const ReminderTemplatesPage: React.FC = () => {
   const { t } = useTranslation();
   const queryClient = useQueryClient();
 
-  // ---- Global toggles ---------------------------------------------------
-  // Only two keys are read on this page — fetch just those instead of
-  // the full ~100-row app_settings dict. Saves transferring + parsing
-  // every unrelated setting.
+  // Global on/off + lead time: owned by the "Pre-event reminder" workflow when
+  // the engine is live; otherwise the legacy crm_event_reminders_* settings drive
+  // the hourly pass, so we keep their controls. Per-event override (disable /
+  // offset / custom body) always lives on the event detail page.
+  const { flags } = useFeatureFlags();
+  const workflowsLive = !!flags.workflows;
+
   const { data: settings } = useQuery({
     queryKey: ['reminder-settings'],
     queryFn: () => settingsService.getSettings([
       'crm_event_reminders_enabled',
       'crm_event_reminders_days_before',
     ]),
+    enabled: !workflowsLive,
   });
   const [enabled, setEnabled] = useState<boolean>(false);
   const [daysBefore, setDaysBefore] = useState<number>(2);
@@ -259,49 +264,51 @@ export const ReminderTemplatesPage: React.FC = () => {
         </h1>
       </div>
 
-      {/* Global toggles strip */}
+      {/* Schedule (on/off + lead time): in Workflows when the engine is live,
+          else the legacy global controls. */}
       <Card className="mb-4">
-        <h3 className="font-semibold text-sm mb-2">
-          {t('reminderTemplates.globalSection', 'Global behaviour')}
-        </h3>
-        <p className="text-xs text-muted-theme mb-3">
-          {t('reminderTemplates.globalHelp',
-            'Off by default — turn on to start sending pre-event reminders. The offset below is the default; each event can override on its detail page.')}
-        </p>
-        <div className="flex items-center gap-6 flex-wrap">
-          <label className="inline-flex items-center gap-2 text-sm cursor-pointer">
-            <input
-              type="checkbox"
-              checked={enabled}
-              onChange={(e) => setEnabled(e.target.checked)}
-            />
-            {t('reminderTemplates.enableLabel', 'Send pre-event reminder emails')}
-          </label>
-          <div className="flex items-center gap-2">
-            <label htmlFor="reminder-days-before" className="text-sm">
-              {t('reminderTemplates.daysBeforeLabel', 'Days before the event')}
-            </label>
-            <Input
-              id="reminder-days-before"
-              type="number"
-              min={0}
-              max={365}
-              value={daysBefore}
-              onChange={(e) => setDaysBefore(Number(e.target.value))}
-              className="w-24"
-            />
+        {workflowsLive ? (
+          <div className="flex items-start gap-2 text-sm text-blue-800 dark:text-blue-200">
+            <WorkflowIcon className="w-4 h-4 mt-0.5 shrink-0" />
+            <div>
+              <p className="font-medium">{t('reminderTemplates.scheduleMoved.title', 'The reminder schedule is now in Workflows')}</p>
+              <p className="mt-1 text-muted-theme">
+                {t('reminderTemplates.scheduleMoved.body', 'Whether pre-event reminders are sent, and how many days before the event, is configured in the “Pre-event reminder” workflow. This page edits the email templates; per-event overrides stay on each event’s detail page.')}{' '}
+                <Link to="/admin/workflows" className="underline font-medium">{t('reminderTemplates.scheduleMoved.link', 'Open Workflows')}</Link>
+              </p>
+            </div>
           </div>
-          <Button
-            variant="outline"
-            size="sm"
-            onClick={() => saveSettingsMutation.mutate()}
-            isLoading={saveSettingsMutation.isPending}
-            disabled={saveSettingsMutation.isPending}
-            leftIcon={<Save className="w-4 h-4" />}
-          >
-            {t('reminderTemplates.saveSettings', 'Save global settings')}
-          </Button>
-        </div>
+        ) : (
+          <>
+            <h3 className="font-semibold text-sm mb-2">
+              {t('reminderTemplates.globalSection', 'Global behaviour')}
+            </h3>
+            <p className="text-xs text-muted-theme mb-3">
+              {t('reminderTemplates.globalHelp',
+                'Off by default — turn on to start sending pre-event reminders. The offset below is the default; each event can override on its detail page.')}
+            </p>
+            <div className="flex items-center gap-6 flex-wrap">
+              <label className="inline-flex items-center gap-2 text-sm cursor-pointer">
+                <input type="checkbox" checked={enabled} onChange={(e) => setEnabled(e.target.checked)} />
+                {t('reminderTemplates.enableLabel', 'Send pre-event reminder emails')}
+              </label>
+              <div className="flex items-center gap-2">
+                <label htmlFor="reminder-days-before" className="text-sm">
+                  {t('reminderTemplates.daysBeforeLabel', 'Days before the event')}
+                </label>
+                <Input id="reminder-days-before" type="number" min={0} max={365}
+                  value={daysBefore} onChange={(e) => setDaysBefore(Number(e.target.value))} className="w-24" />
+              </div>
+              <Button variant="outline" size="sm"
+                onClick={() => saveSettingsMutation.mutate()}
+                isLoading={saveSettingsMutation.isPending}
+                disabled={saveSettingsMutation.isPending}
+                leftIcon={<Save className="w-4 h-4" />}>
+                {t('reminderTemplates.saveSettings', 'Save global settings')}
+              </Button>
+            </div>
+          </>
+        )}
       </Card>
 
       <div className="grid grid-cols-1 lg:grid-cols-3 gap-6">