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/motion/FadeIn.tsx

@@ -0,0 +1,33 @@
+import { motion, type HTMLMotionProps } from 'framer-motion';
+import { forwardRef, type ReactNode } from 'react';
+import { fadeIn, fadeInTransition } from './transitions';
+
+interface FadeInProps extends Omit<HTMLMotionProps<'div'>, 'initial' | 'animate' | 'exit'> {
+  children: ReactNode;
+  delay?: number;
+  duration?: number;
+}
+
+export const FadeIn = forwardRef<HTMLDivElement, FadeInProps>(
+  ({ children, delay = 0, duration, ...props }, ref) => {
+    return (
+      <motion.div
+        ref={ref}
+        variants={fadeIn}
+        initial="initial"
+        animate="animate"
+        exit="exit"
+        transition={{
+          ...fadeInTransition,
+          delay,
+          ...(duration !== undefined && { duration }),
+        }}
+        {...props}
+      >
+        {children}
+      </motion.div>
+    );
+  },
+);
+
+FadeIn.displayName = 'FadeIn';