feat: decouple hero header from gallery layouts (#158)

- Add separate header_style setting (hero/standard/minimal/none) that can
  be combined with any layout type (grid/masonry/carousel/timeline/mosaic)
- Create HeroHeader and HeroDivider components for reusable hero section
- Add hero_divider_style setting (wave/straight/angle/curve/none)
- Add database migration for header_style and hero_divider_style columns
- Remove deprecated HeroGalleryLayout component
- Fix various TypeScript errors across the codebase:
  - Add missing type properties (css_template_id, updatedAt, justified settings)
  - Fix null handling for event_date and expires_at fields
  - Fix translation function calls and i18n config
  - Remove unused imports and variables

frontend/src/pages/admin/AdminDashboard.tsx

@@ -195,7 +195,7 @@ export const AdminDashboard: React.FC = () => {
             ) : (
               <div className="space-y-3">
                 {expiringEvents.slice(0, 5).map((event) => {
-                  const daysLeft = differenceInDays(parseISO(event.expires_at), new Date());
+                  const daysLeft = differenceInDays(parseISO(event.expires_at!), new Date());
                   
                   return (
                     <div
@@ -216,7 +216,7 @@ export const AdminDashboard: React.FC = () => {
                           {t('admin.daysLeft', { count: daysLeft })}
                         </p>
                         <p className="text-xs text-neutral-500">
-                          {t('gallery.expires')} {format(parseISO(event.expires_at), 'PP')}
+                          {t('gallery.expires')} {format(parseISO(event.expires_at!), 'PP')}
                         </p>
                       </div>
                     </div>

frontend/src/pages/admin/CreateEventPage.tsx

@@ -20,6 +20,7 @@ import { eventsService } from '../../services/events.service';
 import { useLocalizedDate } from '../../hooks/useLocalizedDate';
 import { categoriesService } from '../../services/categories.service';
 import { settingsService } from '../../services/settings.service';
+import { publicSettingsService } from '../../services/publicSettings.service';
 import { cssTemplatesService } from '../../services/cssTemplates.service';
 import { eventTypesService } from '../../services/eventTypes.service';
 import { useTranslation } from 'react-i18next';
@@ -152,7 +153,7 @@ export const CreateEventPage: React.FC = () => {
   // Fetch public settings for field requirements
   const { data: publicSettings } = useQuery({
     queryKey: ['public-settings'],
-    queryFn: () => settingsService.getPublicSettings()
+    queryFn: () => publicSettingsService.getPublicSettings()
   });
 
   // Get field requirements (default to true if not set)

frontend/src/pages/admin/EventDetailsPage.tsx

@@ -60,7 +60,7 @@ import { buildResourceUrl } from '../../utils/url';
 import { isGalleryPublic, normalizeRequirePassword } from '../../utils/accessControl';
 import { archiveService } from '../../services/archive.service';
 import { externalMediaService } from '../../services/externalMedia.service';
-import { photosService, AdminPhoto, type PhotoFilters as PhotoFilterParams, type FeedbackFilters, type FilterSummary } from '../../services/photos.service';
+import { photosService, AdminPhoto, type PhotoFilters as PhotoFilterParams, type FeedbackFilters } from '../../services/photos.service';
 import { feedbackService, FeedbackSettings as FeedbackSettingsType } from '../../services/feedback.service';
 import { cssTemplatesService, type EnabledTemplate } from '../../services/cssTemplates.service';
 import { ThemeConfig, GALLERY_THEME_PRESETS } from '../../types/theme.types';
@@ -337,28 +337,6 @@ export const EventDetailsPage: React.FC = () => {
     },
   });
 
-  const applyThemeMutation = useMutation({
-    mutationFn: async ({ theme, presetName }: { theme: ThemeConfig; presetName: string }) => {
-      if (!id) {
-        throw new Error('Missing event identifier');
-      }
-
-      const colorThemeValue = presetName && presetName !== 'custom'
-        ? presetName
-        : JSON.stringify(theme);
-
-      return eventsService.updateEvent(parseInt(id), { color_theme: colorThemeValue });
-    },
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['admin-event', id] });
-      toast.success(t('branding.themeApplied', 'Theme updated'));
-    },
-    onError: (error: any) => {
-      const message = error?.response?.data?.error || t('branding.themeApplyError', 'Failed to apply theme');
-      toast.error(message);
-    }
-  });
-
   // Archive mutation
   const archiveMutation = useMutation({
     mutationFn: () => eventsService.archiveEvent(parseInt(id!)),
@@ -470,7 +448,7 @@ export const EventDetailsPage: React.FC = () => {
     try {
       const formData = new FormData();
       formData.append('logo', file);
-      const response = await api.post(`/admin/events/${id}/logo`, formData, {
+      await api.post(`/admin/events/${id}/logo`, formData, {
         headers: { 'Content-Type': 'multipart/form-data' }
       });
       toast.success(t('events.eventLogoUploaded', 'Event logo uploaded successfully'));
@@ -1745,6 +1723,7 @@ export const EventDetailsPage: React.FC = () => {
                 queryClient.invalidateQueries({ queryKey: ['admin-event', id] });
               }}
               onSelectionChange={setSelectedPhotoIds}
+              categories={categories}
             />
           )}
 

frontend/src/pages/admin/EventTypesPage.tsx

@@ -277,7 +277,7 @@ export const EventTypesPage: React.FC = () => {
       {showCreateModal && (
         <EventTypeModal
           onClose={() => setShowCreateModal(false)}
-          onSubmit={(data) => createMutation.mutate(data)}
+          onSubmit={(data) => createMutation.mutate(data as CreateEventTypeData)}
           isLoading={createMutation.isPending}
         />
       )}

frontend/src/pages/gallery/PreviewPage.tsx

@@ -30,7 +30,7 @@ const mockCategories = [
 export const PreviewPage: React.FC = () => {
   const { setTheme } = useTheme();
   const [brandingSettings, setBrandingSettings] = useState<any>(null);
-  const [selectedCategoryId, setSelectedCategoryId] = useState<number | null>(null);
+  const [selectedCategoryId, setSelectedCategoryId] = useState<number | string | null>(null);
   const [searchTerm, setSearchTerm] = useState('');
   const [sortBy, setSortBy] = useState<'date' | 'name' | 'size' | 'rating'>('date');