feat: P1 Calendar — CalendarView (month/week/list, drag&drop, channel filter)

components/Header.js

@@ -1,7 +1,7 @@
 'use client';
 import Link from 'next/link';
 import { useRouter } from 'next/navigation';
-import { Sparkles, LogOut, Settings2 } from 'lucide-react';
+import { Sparkles, LogOut, Settings2, CalendarDays } from 'lucide-react';
 import ThemeToggle from './ThemeToggle';
 
 export default function Header({ user }) {
@@ -17,6 +17,12 @@ export default function Header({ user }) {
           <Sparkles className="w-5 h-5 text-accent" />
           <span className="font-bold">ZeroPost</span>
         </Link>
+        <nav className="hidden sm:flex items-center gap-1">
+          <Link href="/calendar" className="btn-ghost px-3 py-1.5 text-sm flex items-center gap-1.5">
+            <CalendarDays className="w-4 h-4" />
+            <span>Календарь</span>
+          </Link>
+        </nav>
         <div className="flex items-center gap-2">
           {user?.isAdmin && (
             <Link