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.

duty_teller/handlers/group_duty_pin.py

@@ -87,10 +87,19 @@ def _get_contact_button_markup(lang: str) -> InlineKeyboardMarkup | None:
     Uses a t.me Mini App deep link so the app opens inside Telegram. Uses url (not web_app):
     InlineKeyboardButton with web_app is allowed only in private chats, so in groups
     Telegram returns Button_type_invalid. A plain URL button works everywhere.
+
+    When MINI_APP_SHORT_NAME is set, the URL is a direct Mini App link so the app opens
+    with start_param=duty (current duty view). Otherwise the link is to the bot with
+    ?startapp=duty (user may land in bot chat; opening the app from menu does not pass
+    start_param in some clients).
     """
     if not config.BOT_USERNAME:
         return None
-    url = f"https://t.me/{config.BOT_USERNAME}?startapp=duty"
+    short = (config.MINI_APP_SHORT_NAME or "").strip().strip("/")
+    if short:
+        url = f"https://t.me/{config.BOT_USERNAME}/{short}?startapp=duty"
+    else:
+        url = f"https://t.me/{config.BOT_USERNAME}?startapp=duty"
     button = InlineKeyboardButton(
         text=t(lang, "pin_duty.view_contacts"),
         url=url,