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/lib/telegram-ready.ts

@@ -0,0 +1,25 @@
+/**
+ * Single-call wrapper for Telegram Mini App ready().
+ * Called once when the first visible screen has finished loading so Telegram
+ * hides its native loading animation only after our content is ready.
+ */
+
+import { miniAppReady } from "@telegram-apps/sdk-react";
+
+let readyCalled = false;
+
+/**
+ * Calls Telegram miniAppReady() at most once per session.
+ * Safe when SDK is unavailable (e.g. non-Telegram environment).
+ */
+export function callMiniAppReadyOnce(): void {
+  if (readyCalled) return;
+  try {
+    if (miniAppReady.isAvailable()) {
+      miniAppReady();
+      readyCalled = true;
+    }
+  } catch {
+    // SDK not available or not in Mini App context; no-op.
+  }
+}