fix: comprehensive UI/UX accessibility and usability improvements

Public site: skip-to-content link, mobile menu focus trap + Escape key,
aria-current on nav, keyboard navigation for carousels/tabs/articles,
ARIA roles (tablist/tab/tabpanel, combobox/listbox, region, dialog),
form labels + aria-describedby, 44px touch targets, semantic HTML
(<time>, <del>), prefers-reduced-motion on Hero scroll hijack,
mobile schedule filters, URL hash sync on scroll for correct refresh.

Admin panel: password toggle aria-label, toast aria-live regions,
SelectField keyboard navigation (Arrow/Enter/Escape), aria-invalid
on validation errors, sidebar hamburger aria-label/expanded,
nav aria-label, ArrayEditor aria-expanded on collapsible items.

src/app/admin/hero/page.tsx

@@ -115,6 +115,7 @@ function VideoSlot({
           </div>
           <button
             onClick={onRemove}
+            aria-label={`Удалить видео: ${label}`}
             className="absolute top-2 right-2 rounded-full bg-black/70 p-1.5 text-neutral-400 opacity-0 transition-opacity hover:text-red-400 group-hover:opacity-100"
             title="Удалить"
           >
@@ -300,7 +301,7 @@ function VideoManager({
         )}
       </div>
 
-      <div className="grid gap-4 sm:grid-cols-3">
+      <div className="grid gap-4 sm:grid-cols-3 max-w-3xl">
         {SLOTS.map((slot, i) => (
           <VideoSlot
             key={slot.key}