refactor(slideshow): replace per-event-type preset with a picpeak-wide one

The slideshow display preset (transition / interval / speed / color filter) was
set PER EVENT TYPE in the Edit Event Type dialog. Replace it with a single
picpeak-wide default in Settings -> Slideshow ("Default style for new
slideshows"). New events seed their show_* columns from this global preset
(was: from the event type's slideshow_preset); the per-event override is
unchanged.

- Removed event_types.slideshow_preset usage everywhere (EventTypeModal section,
  eventTypes.service types, eventTypeService whitelist, adminEventTypes
  validators/POST). The DB column from migration 138 is left inert.
- Global preset stored in app_settings (slideshow_interval_ms/transition/
  transition_ms/colorfilter), saved via PUT /admin/settings/slideshow.
- adminEvents create-seeding now reads the global preset (getAppSetting) instead
  of the event type.
- en/de: presetTitle + presetHint.

frontend/src/components/admin/SlideshowGlobalDefaultsCard.tsx

@@ -17,12 +17,18 @@ import {
   SLIDESHOW_WATERMARK_POSITIONS,
   SLIDESHOW_WATERMARK_STYLES,
   SLIDESHOW_FITS,
+  SLIDESHOW_TRANSITIONS,
+  SLIDESHOW_COLORFILTERS,
   type SlideshowGlobalDefaults,
 } from '../../services/slideshow.service';
 import { WatermarkSourcePicker } from './WatermarkSourcePicker';
 
 const DEFAULTS: SlideshowGlobalDefaults = {
   slideshow_fit: 'cover',
+  slideshow_interval_ms: 5000,
+  slideshow_transition: 'crossfade',
+  slideshow_transition_ms: 800,
+  slideshow_colorfilter: 'none',
   slideshow_watermark_enabled: false,
   slideshow_watermark_source: 'logo',
   slideshow_watermark_position: 'bottom-right',
@@ -46,6 +52,10 @@ export const SlideshowGlobalDefaultsCard: React.FC = () => {
       if (cancelled || !s) return;
       setVal({
         slideshow_fit: s.slideshow_fit ?? DEFAULTS.slideshow_fit,
+        slideshow_interval_ms: s.slideshow_interval_ms ?? DEFAULTS.slideshow_interval_ms,
+        slideshow_transition: s.slideshow_transition ?? DEFAULTS.slideshow_transition,
+        slideshow_transition_ms: s.slideshow_transition_ms ?? DEFAULTS.slideshow_transition_ms,
+        slideshow_colorfilter: s.slideshow_colorfilter ?? DEFAULTS.slideshow_colorfilter,
         slideshow_watermark_enabled: s.slideshow_watermark_enabled ?? DEFAULTS.slideshow_watermark_enabled,
         slideshow_watermark_source: s.slideshow_watermark_source ?? DEFAULTS.slideshow_watermark_source,
         slideshow_watermark_position: s.slideshow_watermark_position ?? DEFAULTS.slideshow_watermark_position,
@@ -99,6 +109,65 @@ export const SlideshowGlobalDefaultsCard: React.FC = () => {
           </p>
         </div>
 
+        {/* Default display style new slideshows inherit (override per event) */}
+        <div className="pt-2 border-t border-neutral-200 dark:border-neutral-700">
+          <p className="text-sm font-medium text-neutral-700 dark:text-neutral-300 mb-1">
+            {t('slideshow.presetTitle', 'Default style for new slideshows')}
+          </p>
+          <p className="text-xs text-neutral-500 dark:text-neutral-400 mb-3">
+            {t('slideshow.presetHint', 'Applied to events created from now on; each event can still override it.')}
+          </p>
+          <div className="grid grid-cols-1 sm:grid-cols-3 gap-3">
+            <div>
+              <label className={labelClass}>{t('slideshow.transitionLabel', 'Transition')}</label>
+              <select
+                value={val.slideshow_transition}
+                onChange={(e) => setVal({ ...val, slideshow_transition: e.target.value as SlideshowGlobalDefaults['slideshow_transition'] })}
+                className={inputClass}
+              >
+                {SLIDESHOW_TRANSITIONS.map((tr) => (
+                  <option key={tr} value={tr}>{t(`slideshow.transition.${tr}`, tr)}</option>
+                ))}
+              </select>
+            </div>
+            <div>
+              <label className={labelClass}>{t('slideshow.intervalLabel', 'Display time (sec)')}</label>
+              <input
+                type="number"
+                min={1}
+                max={120}
+                value={Math.round(val.slideshow_interval_ms / 1000)}
+                onChange={(e) => setVal({ ...val, slideshow_interval_ms: Math.min(120, Math.max(1, parseInt(e.target.value, 10) || 5)) * 1000 })}
+                className={inputClass}
+              />
+            </div>
+            <div>
+              <label className={labelClass}>{t('slideshow.transitionSpeedLabel', 'Transition speed (ms)')}</label>
+              <input
+                type="number"
+                min={100}
+                max={5000}
+                step={100}
+                value={val.slideshow_transition_ms}
+                onChange={(e) => setVal({ ...val, slideshow_transition_ms: Math.min(5000, Math.max(100, parseInt(e.target.value, 10) || 800)) })}
+                className={inputClass}
+              />
+            </div>
+            <div>
+              <label className={labelClass}>{t('slideshow.colorfilterLabel', 'Color filter')}</label>
+              <select
+                value={val.slideshow_colorfilter}
+                onChange={(e) => setVal({ ...val, slideshow_colorfilter: e.target.value as SlideshowGlobalDefaults['slideshow_colorfilter'] })}
+                className={inputClass}
+              >
+                {SLIDESHOW_COLORFILTERS.map((cf) => (
+                  <option key={cf} value={cf}>{t(`slideshow.colorfilter.${cf}`, cf)}</option>
+                ))}
+              </select>
+            </div>
+          </div>
+        </div>
+
         <div className="pt-2 border-t border-neutral-200 dark:border-neutral-700">
         <label className="flex items-start gap-2">
           <input

frontend/src/i18n/locales/de.json

@@ -3214,6 +3214,8 @@
       "contain": "Schwarze Balken (kein Beschnitt)"
     },
     "fitHint": "„Füllen“ beschneidet das Bild zum Ausfüllen; „Schwarze Balken“ zeigt das ganze Foto – besser für Hochformat.",
+    "presetTitle": "Standard-Stil für neue Diashows",
+    "presetHint": "Gilt für ab jetzt erstellte Events; jedes Event kann ihn weiterhin überschreiben.",
     "defaultsSaved": "Diashow-Vorgaben gespeichert",
     "liveHint": "Änderungen werden in einer laufenden Diashow innerhalb weniger Sekunden übernommen – der Link muss nicht neu erstellt werden.",
     "saveSettings": "Diashow-Einstellungen speichern",

frontend/src/i18n/locales/en.json

@@ -3238,6 +3238,8 @@
       "contain": "Black bars (no crop)"
     },
     "fitHint": "\"Fill\" crops to fill the screen; \"Black bars\" shows the whole photo — better for portrait images.",
+    "presetTitle": "Default style for new slideshows",
+    "presetHint": "Applied to events created from now on; each event can still override it.",
     "defaultsSaved": "Slideshow defaults saved",
     "liveHint": "Changes apply to a running slideshow within a few seconds — no need to regenerate the link.",
     "saveSettings": "Save slideshow settings",

frontend/src/pages/admin/EventTypesPage.tsx

@@ -18,21 +18,6 @@ import {
 import { Button, Input, Card, Loading } from '../../components/common';
 import { eventTypesService, EventType, CreateEventTypeData, UpdateEventTypeData } from '../../services/eventTypes.service';
 import { GALLERY_THEME_PRESETS } from '../../types/theme.types';
-import { SlideshowStyleFields } from '../../components/admin/SlideshowStyleFields';
-import { DEFAULT_SLIDESHOW_STYLE, type SlideshowStyle } from '../../services/slideshow.service';
-import { useFeatureEnabled } from '../../contexts/FeatureFlagsContext';
-
-// Parse a type's stored slideshow_preset (JSON string | object | null) into a
-// full SlideshowStyle, falling back to defaults for any missing keys.
-function parseSlideshowPreset(raw: EventType['slideshow_preset']): SlideshowStyle {
-  if (!raw) return { ...DEFAULT_SLIDESHOW_STYLE };
-  try {
-    const obj = typeof raw === 'string' ? JSON.parse(raw) : raw;
-    return { ...DEFAULT_SLIDESHOW_STYLE, ...obj };
-  } catch {
-    return { ...DEFAULT_SLIDESHOW_STYLE };
-  }
-}
 
 // Common emoji options for event types
 const EMOJI_OPTIONS = [
@@ -336,7 +321,6 @@ const EventTypeModal: React.FC<EventTypeModalProps> = ({
 }) => {
   const { t } = useTranslation();
   const isEditing = !!eventType;
-  const slideshowEnabled = useFeatureEnabled('slideshow');
 
   const [form, setForm] = useState<CreateEventTypeData>({
     name: eventType?.name || '',
@@ -345,12 +329,6 @@ const EventTypeModal: React.FC<EventTypeModalProps> = ({
     theme_preset: eventType?.theme_preset || 'default'
   });
 
-  // Slideshow preset new events of this type inherit. Edited via the shared
-  // <SlideshowStyleFields>; serialized into slideshow_preset on submit.
-  const [slideshowStyle, setSlideshowStyle] = useState<SlideshowStyle>(
-    () => parseSlideshowPreset(eventType?.slideshow_preset)
-  );
-
   const [errors, setErrors] = useState<Partial<Record<keyof CreateEventTypeData, string>>>({});
 
   const handleSubmit = (e: React.FormEvent) => {
@@ -379,11 +357,9 @@ const EventTypeModal: React.FC<EventTypeModalProps> = ({
       if (form.slug_prefix !== eventType?.slug_prefix) updates.slug_prefix = form.slug_prefix;
       if (form.emoji !== eventType?.emoji) updates.emoji = form.emoji;
       if (form.theme_preset !== eventType?.theme_preset) updates.theme_preset = form.theme_preset;
-      const originalStyle = JSON.stringify(parseSlideshowPreset(eventType?.slideshow_preset));
-      if (slideshowEnabled && JSON.stringify(slideshowStyle) !== originalStyle) updates.slideshow_preset = slideshowStyle;
       onSubmit(updates);
     } else {
-      onSubmit({ ...form, ...(slideshowEnabled ? { slideshow_preset: slideshowStyle } : {}) });
+      onSubmit(form);
     }
   };
 
@@ -484,22 +460,6 @@ const EventTypeModal: React.FC<EventTypeModalProps> = ({
                 </select>
               </div>
 
-              {/* Live Slideshow preset (migration 138). New events of this type
-                  inherit these slideshow defaults; admins can still override
-                  per event on the event detail page. Gated behind the
-                  `slideshow` feature flag. */}
-              {slideshowEnabled && (
-              <div className="pt-2 border-t border-neutral-200 dark:border-neutral-700">
-                <label className="block text-sm font-medium text-neutral-700 dark:text-neutral-300 mb-1">
-                  {t('eventTypes.form.slideshowPreset', 'Slideshow preset')}
-                </label>
-                <p className="text-xs text-neutral-500 dark:text-neutral-400 mb-3">
-                  {t('eventTypes.form.slideshowPresetHint', 'Default slideshow style for new events of this type.')}
-                </p>
-                <SlideshowStyleFields value={slideshowStyle} onChange={setSlideshowStyle} />
-              </div>
-              )}
-
               {/* Active toggle for editing */}
               {isEditing && (
                 <label className="flex items-center gap-3 pt-2">

frontend/src/services/eventTypes.service.ts

@@ -4,7 +4,6 @@
  */
 
 import { api } from '../config/api';
-import type { SlideshowStyle } from './slideshow.service';
 
 export interface EventType {
   id: number;
@@ -13,9 +12,6 @@ export interface EventType {
   emoji: string;
   theme_preset: string;
   theme_config: string | null;
-  // Live Slideshow preset new events of this type inherit (migration 138).
-  // Stored as a JSON string by the API; null = no preset.
-  slideshow_preset: string | null;
   display_order: number;
   is_system: boolean;
   is_active: boolean;
@@ -29,7 +25,6 @@ export interface CreateEventTypeData {
   emoji?: string;
   theme_preset?: string;
   theme_config?: Record<string, unknown>;
-  slideshow_preset?: SlideshowStyle | null;
   display_order?: number;
 }
 
@@ -39,7 +34,6 @@ export interface UpdateEventTypeData {
   emoji?: string;
   theme_preset?: string;
   theme_config?: Record<string, unknown>;
-  slideshow_preset?: SlideshowStyle | null;
   display_order?: number;
   is_active?: boolean;
 }

frontend/src/services/slideshow.service.ts

@@ -24,13 +24,13 @@ export const SLIDESHOW_COLORFILTERS: SlideshowColorFilter[] = ['none', 'bw', 'se
 export const SLIDESHOW_WATERMARK_SOURCES: SlideshowWatermarkSource[] = ['logo', 'logo_dark', 'favicon', 'event'];
 export const SLIDESHOW_WATERMARK_POSITIONS: SlideshowWatermarkPosition[] = ['top-left', 'top-right', 'bottom-left', 'bottom-right'];
 
-// Canonical editable style shape, shared by the per-event card and the
-// per-event-type preset editor. The per-event-type `slideshow_preset` JSON
-// uses exactly these keys; the per-event API maps them to `show_*` columns.
+// Per-event editable style (the override). The picpeak-wide DEFAULT for these
+// lives in the global Settings → Slideshow tab; new events inherit it and the
+// per-event card maps these to `show_*` columns.
 //
 // NOTE: the watermark LOOK (logo/position/opacity/style/size) lives ONLY in the
-// global Settings → Slideshow tab — it is not duplicated here. Per-event/type
-// carry just the `watermark` MODE (inherit/on/off), i.e. the override structure.
+// global tab — not duplicated here. Per-event carries just the `watermark` MODE
+// (inherit/on/off), i.e. the override structure.
 export interface SlideshowStyle {
   interval_ms: number;
   transition: SlideshowTransition;
@@ -53,6 +53,11 @@ export const DEFAULT_SLIDESHOW_STYLE: SlideshowStyle = {
 export interface SlideshowGlobalDefaults {
   // How slides fill the screen (fill+crop vs letterbox/black bars).
   slideshow_fit: SlideshowFit;
+  // Picpeak-wide display preset (default style new events inherit).
+  slideshow_interval_ms: number;
+  slideshow_transition: SlideshowTransition;
+  slideshow_transition_ms: number;
+  slideshow_colorfilter: SlideshowColorFilter;
   slideshow_watermark_enabled: boolean;
   slideshow_watermark_source: SlideshowWatermarkSource;
   slideshow_watermark_position: SlideshowWatermarkPosition;