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/app/page.tsx

@@ -0,0 +1,50 @@
+/**
+ * Main Mini App page: current duty deep link or calendar view.
+ * Delegates to CurrentDutyView or CalendarPage; runs theme and app init.
+ */
+
+"use client";
+
+import { useCallback } from "react";
+import { useAppStore } from "@/store/app-store";
+import { useShallow } from "zustand/react/shallow";
+import { useTelegramTheme } from "@/hooks/use-telegram-theme";
+import { useTelegramAuth } from "@/hooks/use-telegram-auth";
+import { useAppInit } from "@/hooks/use-app-init";
+import { CurrentDutyView } from "@/components/current-duty/CurrentDutyView";
+import { CalendarPage } from "@/components/CalendarPage";
+
+export default function Home() {
+  useTelegramTheme();
+
+  const { initDataRaw, startParam, isLocalhost } = useTelegramAuth();
+  const isAllowed = isLocalhost || !!initDataRaw;
+
+  useAppInit({ isAllowed, startParam });
+
+  const { currentView, setCurrentView, setSelectedDay } = useAppStore(
+    useShallow((s) => ({
+      currentView: s.currentView,
+      setCurrentView: s.setCurrentView,
+      setSelectedDay: s.setSelectedDay,
+    }))
+  );
+
+  const handleBackFromCurrentDuty = useCallback(() => {
+    setCurrentView("calendar");
+    setSelectedDay(null);
+  }, [setCurrentView, setSelectedDay]);
+
+  if (currentView === "currentDuty") {
+    return (
+      <div className="mx-auto flex min-h-screen w-full max-w-[var(--max-width-app)] flex-col bg-background px-3 pb-6 pt-safe">
+        <CurrentDutyView
+          onBack={handleBackFromCurrentDuty}
+          openedFromPin={startParam === "duty"}
+        />
+      </div>
+    );
+  }
+
+  return <CalendarPage isAllowed={isAllowed} initDataRaw={initDataRaw} />;
+}