Add Next.js frontend PWA

- Pages: login, register, tasks list, task detail
- Components: TaskCard, TaskForm, GroupSelector, StatusBadge, Header
- Tailwind CSS, dark/light mode, PWA manifest
- Running on :3001 via systemd

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/tasks/components/Header.tsx

@@ -0,0 +1,64 @@
+"use client";
+
+import { useAuth } from "@/lib/auth";
+import { useTheme } from "./ThemeProvider";
+import Link from "next/link";
+import { useRouter } from "next/navigation";
+
+export default function Header() {
+  const { user, logout, token } = useAuth();
+  const { theme, toggleTheme } = useTheme();
+  const router = useRouter();
+
+  function handleLogout() {
+    logout();
+    router.push("/login");
+  }
+
+  return (
+    <header className="sticky top-0 z-50 bg-white/80 dark:bg-gray-950/80 backdrop-blur-md border-b border-gray-200 dark:border-gray-800">
+      <div className="max-w-4xl mx-auto px-4 h-14 flex items-center justify-between">
+        <Link href="/tasks" className="text-lg font-bold tracking-tight">
+          Task Team
+        </Link>
+
+        <div className="flex items-center gap-3">
+          <button
+            onClick={toggleTheme}
+            className="p-2 rounded-lg hover:bg-gray-100 dark:hover:bg-gray-800 transition-colors"
+            aria-label="Prepnout tema"
+          >
+            {theme === "dark" ? (
+              <svg className="w-5 h-5" fill="none" viewBox="0 0 24 24" stroke="currentColor">
+                <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M12 3v1m0 16v1m9-9h-1M4 12H3m15.364 6.364l-.707-.707M6.343 6.343l-.707-.707m12.728 0l-.707.707M6.343 17.657l-.707.707M16 12a4 4 0 11-8 0 4 4 0 018 0z" />
+              </svg>
+            ) : (
+              <svg className="w-5 h-5" fill="none" viewBox="0 0 24 24" stroke="currentColor">
+                <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M20.354 15.354A9 9 0 018.646 3.646 9.003 9.003 0 0012 21a9.003 9.003 0 008.354-5.646z" />
+              </svg>
+            )}
+          </button>
+
+          {token && user ? (
+            <div className="flex items-center gap-2">
+              <span className="text-sm text-muted hidden sm:inline">{user.name || user.email}</span>
+              <button
+                onClick={handleLogout}
+                className="text-sm px-3 py-1.5 rounded-lg border border-gray-300 dark:border-gray-600 hover:bg-gray-50 dark:hover:bg-gray-800 transition-colors"
+              >
+                Odhlasit
+              </button>
+            </div>
+          ) : (
+            <Link
+              href="/login"
+              className="text-sm px-3 py-1.5 rounded-lg bg-blue-600 text-white hover:bg-blue-700 transition-colors"
+            >
+              Prihlasit
+            </Link>
+          )}
+        </div>
+      </div>
+    </header>
+  );
+}