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.

docs/configuration.md

@@ -7,6 +7,7 @@ All configuration is read from the environment (e.g. `.env` via python-dotenv).
 | **BOT_TOKEN** | string | *(empty)* | Telegram bot token from [@BotFather](https://t.me/BotFather). Required for the bot to run; if unset, the entry point exits with a clear message. The server that serves the Mini App API must use the **same** token as the bot; otherwise initData validation returns `hash_mismatch`. |
 | **DATABASE_URL** | string (SQLAlchemy URL) | `sqlite:///data/duty_teller.db` | Database connection URL. Should start with `sqlite://` or `postgresql://`; a warning is logged at startup if the format is unexpected. Example: `sqlite:///data/duty_teller.db`. |
 | **MINI_APP_BASE_URL** | string (URL, no trailing slash) | *(empty)* | Base URL of the miniapp (for documentation and CORS). Trailing slash is stripped. Example: `https://your-domain.com/app`. |
+| **MINI_APP_SHORT_NAME** | string | *(empty)* | Short name of the Web App in BotFather (e.g. `DutyApp`). When set, the pinned duty message "View contacts" button uses a direct Mini App link `https://t.me/BotName/ShortName?startapp=duty` so the app opens on the current-duty view. If unset, the button uses `https://t.me/BotName?startapp=duty` (user may land in bot chat first). |
 | **HTTP_HOST** | string | `127.0.0.1` | Host to bind the HTTP server to. Use `127.0.0.1` to listen only on localhost; use `0.0.0.0` to accept connections from all interfaces (e.g. when behind a reverse proxy on another machine). |
 | **HTTP_PORT** | integer (1–65535) | `8080` | Port for the HTTP server (FastAPI + static webapp). Invalid or out-of-range values are clamped; non-numeric values fall back to 8080. |
 | **ALLOWED_USERNAMES** | comma-separated list | *(empty)* | **Not used for access.** Kept for reference only. Access to the miniapp is controlled by **roles in the DB** (assigned by an admin via `/set_role`). |