feat: MC admin — collapsible cards, filters, photo preview, validation, archive

- Collapsible cards with title + hall in label, archive badge
- Archived MCs sorted to bottom, dimmed with "Архив" badge
- Cards have hover + focus-within gold border highlight
- Date validation: error text for missing dates and invalid time ranges
- Search by title/trainer + filter by date (upcoming/past) and hall
- Photo preview with hover overlay (like trainer page)
- ArrayEditor: hiddenItems, getItemBadge props, focus-within styles

src/app/admin/_components/ArrayEditor.tsx

@@ -13,6 +13,8 @@ interface ArrayEditorProps<T> {
   addLabel?: string;
   collapsible?: boolean;
   getItemTitle?: (item: T, index: number) => string;
+  getItemBadge?: (item: T, index: number) => React.ReactNode;
+  hiddenItems?: Set<number>;
 }
 
 export function ArrayEditor<T>({
@@ -24,6 +26,8 @@ export function ArrayEditor<T>({
   addLabel = "Добавить",
   collapsible = false,
   getItemTitle,
+  getItemBadge,
+  hiddenItems,
 }: ArrayEditorProps<T>) {
   const [dragIndex, setDragIndex] = useState<number | null>(null);
   const [insertAt, setInsertAt] = useState<number | null>(null);
@@ -146,14 +150,15 @@ export function ArrayEditor<T>({
     if (dragIndex === null || insertAt === null) {
       return items.map((item, i) => {
         const isCollapsed = collapsible && collapsed.has(i) && newItemIndex !== i;
+        const isHidden = hiddenItems?.has(i) ?? false;
         const title = getItemTitle?.(item, i) || `#${i + 1}`;
         return (
           <div
             key={i}
             ref={(el) => { itemRefs.current[i] = el; }}
-            className={`rounded-lg border bg-neutral-900/50 mb-3 hover:border-white/25 hover:bg-neutral-800/50 transition-all ${
+            className={`rounded-lg border bg-neutral-900/50 mb-3 hover:border-white/25 hover:bg-neutral-800/50 focus-within:border-gold/50 focus-within:bg-neutral-800 transition-all ${
               newItemIndex === i ? "border-gold/40 ring-1 ring-gold/20" : "border-white/10"
-            }`}
+            } ${isHidden ? "hidden" : ""}`}
           >
             <div className={`flex items-center justify-between gap-2 p-4 ${isCollapsed ? "" : "pb-0 mb-3"}`}>
               <div className="flex items-center gap-2 flex-1 min-w-0">
@@ -170,6 +175,7 @@ export function ArrayEditor<T>({
                     className="flex items-center gap-2 flex-1 min-w-0 text-left cursor-pointer group"
                   >
                     <span className="text-sm font-medium text-neutral-300 truncate group-hover:text-white transition-colors">{title}</span>
+                    {getItemBadge?.(item, i)}
                     <ChevronDown size={14} className={`text-neutral-500 transition-transform duration-200 shrink-0 ${isCollapsed ? "" : "rotate-180"}`} />
                   </button>
                 )}
@@ -231,7 +237,7 @@ export function ArrayEditor<T>({
         <div
           key={i}
           ref={(el) => { itemRefs.current[i] = el; }}
-          className="rounded-lg border border-white/10 bg-neutral-900/50 p-4 mb-3 hover:border-white/25 hover:bg-neutral-800/50 transition-colors"
+          className="rounded-lg border border-white/10 bg-neutral-900/50 p-4 mb-3 hover:border-white/25 hover:bg-neutral-800/50 focus-within:border-gold/50 focus-within:bg-neutral-800 transition-colors"
         >
           <div className="flex items-start justify-between gap-2 mb-3">
             <div