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/components/providers/TelegramProvider.tsx

@@ -0,0 +1,46 @@
+"use client";
+
+import { useEffect } from "react";
+import {
+  init,
+  mountMiniAppSync,
+  mountThemeParamsSync,
+  bindThemeParamsCssVars,
+} from "@telegram-apps/sdk-react";
+import { fixSurfaceContrast } from "@/hooks/use-telegram-theme";
+
+/**
+ * Wraps the app with Telegram Mini App SDK initialization.
+ * Calls init(acceptCustomStyles), mounts theme params (binds --tg-theme-* CSS vars),
+ * and mounts the mini app. Does not call ready() here — the app calls
+ * callMiniAppReadyOnce() from lib/telegram-ready when the first visible screen
+ * has finished loading, so Telegram keeps its native loading animation until then.
+ * Theme is set before first paint by the inline script in layout.tsx (URL hash);
+ * useTelegramTheme() in the app handles ongoing theme changes.
+ */
+export function TelegramProvider({
+  children,
+}: {
+  children: React.ReactNode;
+}) {
+  useEffect(() => {
+    const cleanup = init({ acceptCustomStyles: true });
+
+    if (mountThemeParamsSync.isAvailable()) {
+      mountThemeParamsSync();
+    }
+    if (bindThemeParamsCssVars.isAvailable()) {
+      bindThemeParamsCssVars();
+    }
+    fixSurfaceContrast();
+    void document.documentElement.offsetHeight;
+
+    if (mountMiniAppSync.isAvailable()) {
+      mountMiniAppSync();
+    }
+
+    return cleanup;
+  }, []);
+
+  return <>{children}</>;
+}