feat: migrate to Next.js for Mini App and enhance project structure

- Replaced the previous webapp with a new Mini App built using Next.js, improving performance and maintainability.
- Updated the `.gitignore` to exclude Next.js build artifacts and node modules.
- Revised documentation in `AGENTS.md`, `README.md`, and `architecture.md` to reflect the new Mini App structure and technology stack.
- Enhanced Dockerfile to support the new build process for the Next.js application.
- Updated CI workflow to build and test the Next.js application.
- Added new configuration options for the Mini App, including `MINI_APP_SHORT_NAME` for improved deep linking.
- Refactored frontend testing setup to accommodate the new structure and testing framework.
- Removed legacy webapp files and dependencies to streamline the project.

webapp-next/src/hooks/use-auto-refresh.ts

@@ -0,0 +1,29 @@
+/**
+ * 60-second interval to refresh duty list when viewing the current month.
+ * Replaces state.todayRefreshInterval from webapp/js/main.js.
+ */
+
+"use client";
+
+import { useEffect, useRef } from "react";
+
+const AUTO_REFRESH_INTERVAL_MS = 60000;
+
+/**
+ * When isCurrentMonth is true, calls refresh() immediately, then every 60 seconds.
+ * When isCurrentMonth becomes false or on unmount, the interval is cleared.
+ */
+export function useAutoRefresh(
+  refresh: () => void,
+  isCurrentMonth: boolean
+): void {
+  const refreshRef = useRef(refresh);
+  refreshRef.current = refresh;
+
+  useEffect(() => {
+    if (!isCurrentMonth) return;
+    refreshRef.current();
+    const id = setInterval(() => refreshRef.current(), AUTO_REFRESH_INTERVAL_MS);
+    return () => clearInterval(id);
+  }, [isCurrentMonth]);
+}