fix: address bugs and feature requests from discussion #317

- Share link: display and copy now use the absolute URL built from the
  current origin instead of the relative path stored in events.share_link.
  Added a Copy Link button to the events list (inline + dropdown).
- Detect dev tools default: event creation now reads the global
  enable_devtools_protection app setting instead of always falling back to
  the column default; admins who disable it globally get new events with
  it disabled too.
- Require password default: added a global "Require password by default"
  setting (event_default_require_password, default true), exposed via
  Settings -> Events. Create-event form initialises from it.
- Filter bar: added gallery_show_filter_bar setting and hide the search/
  sort row in the public gallery when off, or when the gallery has zero
  photos (fixes the empty-state UX from the screenshot).
- Theme picker unclickable on Create Event: memoised availableEventTypes
  so its identity is stable. The "auto-apply event-type recommended
  preset" effect was firing on every render due to the unstable array
  reference and silently overwriting the user's preset selection ~1ms
  after each click.
- Branding logo disappearing on theme change: handlePresetChange and
  handleThemeChange no longer wipe the existing logoUrl when a preset
  config (which carries no logoUrl) is applied; handleSave falls back to
  brandingSettings.logo_url. themeMutation now invalidates the
  admin-settings and public-settings caches so saved theme changes appear
  immediately.

frontend/src/components/gallery/GalleryView.tsx

@@ -847,8 +847,11 @@ export const GalleryView: React.FC<GalleryViewProps> = ({ slug, event }) => {
           </div>
         )}
 
-        {/* Search and Filters - Only for grid layout */}
-        {!showSidebar ? (
+        {/* Search and Filters - Only for grid layout, when admin enables the
+            filter bar globally, and when the gallery actually has photos
+            (avoids the empty "Search photos by filename" row in the screenshot
+            from discussion #317). */}
+        {!showSidebar && settingsData?.gallery_show_filter_bar !== false && (data?.photos?.length ?? 0) > 0 ? (
           <div className="mt-6">
             <PhotoFilterBar
               categories={data.categories}