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/components/sections/MasterClasses.tsx

@@ -127,11 +127,11 @@ function MasterClassCard({
       <div className="absolute inset-x-0 bottom-0 flex flex-col p-5 sm:p-6">
         {/* Tags row */}
         <div className="flex flex-wrap items-center gap-2 mb-3">
-          <span className="inline-flex items-center gap-1 rounded-full border border-gold/40 bg-black/40 px-2.5 py-0.5 text-[11px] font-semibold uppercase tracking-wider text-gold backdrop-blur-md">
+          <span className="inline-flex items-center gap-1 rounded-full border border-gold/40 bg-black/40 px-2.5 py-0.5 text-xs font-semibold uppercase tracking-wider text-gold backdrop-blur-md">
             {item.style}
           </span>
           {duration && (
-            <span className="inline-flex items-center gap-1 rounded-full bg-white/10 px-2.5 py-0.5 text-[11px] text-white/60 backdrop-blur-md">
+            <span className="inline-flex items-center gap-1 rounded-full bg-white/10 px-2.5 py-0.5 text-xs text-white/60 backdrop-blur-md">
               <Clock size={10} />
               {duration}
             </span>
@@ -168,7 +168,7 @@ function MasterClassCard({
 
         {/* Spots info */}
         {(maxP > 0 || (item.minParticipants && item.minParticipants > 0)) && (
-          <div className="mb-3 flex items-center gap-3 text-[11px]">
+          <div className="mb-3 flex items-center gap-3 text-xs">
             {maxP > 0 && (
               <span className={isFull ? "text-amber-400" : "text-white/40"}>
                 {currentRegs}/{maxP} мест
@@ -186,6 +186,7 @@ function MasterClassCard({
         <div className="flex items-center gap-3">
           <button
             onClick={onSignup}
+            aria-label={`Записаться на ${item.title}`}
             className={`flex-1 rounded-xl py-3 text-sm font-bold uppercase tracking-wide transition-all cursor-pointer ${
               isFull
                 ? "bg-amber-500/15 text-amber-400 hover:bg-amber-500/25"