Fix mobile responsiveness across all pages

- PosPage: rooms list becomes horizontal scroll row on mobile instead of w-56 sidebar
- AvailabilityPage: edit panel stacks below grid on mobile (was fixed w-80 side panel)
- UsersPage roles tab: sidebar stacks above permissions on mobile
- All page containers: p-6 → p-4 md:p-6 (TariffsPage, DiscountsPage, MaintenancePage, ReportsPage, DynamicPricingPage, GuestsPage, LoyaltyPage)
- Stats grids: lg:grid-cols-4 → md:grid-cols-4 (GuestsPage, TariffsPage, DiscountsPage, MaintenancePage, ReportsPage, LoyaltyPage)
- Modal form grids: grid-cols-3 → grid-cols-1 sm:grid-cols-3, grid-cols-5 → grid-cols-3 sm:grid-cols-5, grid-cols-4 → grid-cols-2 sm:grid-cols-4
- PosPage modals: fixed w-80/w-96 → responsive w-[calc(100vw-2rem)] sm:w-80/96

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/pages/DiscountsPage.tsx

@@ -140,8 +140,8 @@ function DiscountModal({
       }
     >
       <div className="space-y-4">
-        <div className="grid grid-cols-3 gap-3">
-          <div className="col-span-2">
+        <div className="grid grid-cols-1 sm:grid-cols-3 gap-3">
+          <div className="sm:col-span-2">
             <label className="block text-sm font-medium text-slate-700 dark:text-slate-300 mb-1.5">Название *</label>
             <input type="text" className="input" placeholder="Корпоративная скидка"
               value={form.name} onChange={e => set('name', e.target.value)} />
@@ -285,7 +285,7 @@ export function DiscountsPage() {
     setDiscounts(prev => prev.map(d => d.id === id ? { ...d, isActive: !d.isActive } : d))
 
   return (
-    <div className="p-6 space-y-6">
+    <div className="p-4 md:p-6 space-y-6">
       {/* Header */}
       <div className="flex items-center justify-between">
         <div>
@@ -301,7 +301,7 @@ export function DiscountsPage() {
       </div>
 
       {/* Stats */}
-      <div className="grid grid-cols-2 lg:grid-cols-4 gap-3">
+      <div className="grid grid-cols-2 md:grid-cols-4 gap-3">
         {[
           { label: 'Всего скидок',  value: discounts.length },
           { label: 'Активных',      value: discounts.filter(d => d.isActive).length },