feat: Linear-style UI redesign with improved mobile experience

Major changes:
- Redesign cabinet with Linear-style components and top navigation
- Replace detail modals with dedicated pages (users, broadcasts, email templates)
- Add email channel support for broadcasts
- Remove pull-to-refresh, improve drag-and-drop on touch devices
- Fix Telegram Mini App: fullscreen, back button, scroll restoration
- Unify admin pages color scheme to design system
- Mobile-first improvements: horizontal tabs for settings, better touch targets

src/components/admin/AdminLayout.tsx

@@ -0,0 +1,61 @@
+import { motion } from 'framer-motion';
+import type { Transition, Variants } from 'framer-motion';
+import type { ReactNode } from 'react';
+
+/**
+ * Centralized animation config for all admin pages.
+ * Change animations here to affect all admin pages at once.
+ */
+export const adminPageTransition: Transition = {
+  duration: 0.15,
+  ease: [0.16, 1, 0.3, 1] as const, // easeOutExpo
+};
+
+export const adminPageVariants: Variants = {
+  initial: { opacity: 0 },
+  animate: { opacity: 1 },
+  exit: { opacity: 0 },
+};
+
+interface AdminLayoutProps {
+  children: ReactNode;
+  className?: string;
+}
+
+/**
+ * AdminLayout - wrapper for all admin pages with consistent animations.
+ * Use this to wrap admin page content for unified transitions.
+ */
+export function AdminLayout({ children, className }: AdminLayoutProps) {
+  return (
+    <motion.div
+      variants={adminPageVariants}
+      initial="initial"
+      animate="animate"
+      exit="exit"
+      transition={adminPageTransition}
+      className={className}
+    >
+      {children}
+    </motion.div>
+  );
+}
+
+/**
+ * Admin content animations for lists and cards.
+ * Use with staggered children.
+ */
+export const adminStaggerContainer: Variants = {
+  initial: {},
+  animate: {
+    transition: {
+      staggerChildren: 0.03,
+    },
+  },
+};
+
+export const adminStaggerItem: Variants = {
+  initial: { opacity: 0 },
+  animate: { opacity: 1 },
+  exit: { opacity: 0 },
+};