feat: enhance Mini App design guidelines and refactor layout components

- Updated Mini App design guidelines to include detailed instructions on UI changes, accessibility rules, and verification processes.
- Refactored multiple components to utilize `MiniAppScreen` and `MiniAppScreenContent` for consistent layout structure across the application.
- Improved error handling in `GlobalError` and `NotFound` components by integrating new layout components for better user experience.
- Introduced new hooks for admin functionality, streamlining access checks and data loading processes.
- Enhanced documentation to reflect changes in design policies and component usage, ensuring clarity for future development.

AGENTS.md

@@ -50,5 +50,5 @@ Docstrings and code comments must be in English (Google-style docstrings). UI st
 - **Config:** Environment variables (e.g. `.env`); no hardcoded secrets.
 - **Database:** One logical transaction per `session_scope` — a single `commit` at the end of the business operation (e.g. in `run_import`). Repository helpers used inside such a flow (e.g. `get_or_create_user_by_full_name`) accept `commit=False` and let the caller commit once.
 - **Error handling:** Do not send `str(exception)` from parsers or DB to the user. Use generic i18n keys (e.g. `import.parse_error_generic`, `import.import_error_generic`) and log the full exception server-side.
-- **Mini App (webapp-next):** When adding or changing UI in `webapp-next/`, follow the [Mini App design guideline](docs/miniapp-design.md): use only design tokens and Tailwind aliases from it, apply layout/safe-area/accessibility rules, and use the checklist for new screens or components.
+- **Mini App (webapp-next):** When adding or changing UI in `webapp-next/`, follow the [Mini App design guideline](docs/miniapp-design.md): use only design tokens and Tailwind aliases, use shared Mini App screen shells, keep Telegram SDK access behind `src/hooks/telegram/*`, apply safe-area/content-safe-area and accessibility rules, and run the Mini App verification matrix (light/dark, iOS/Android safe area, low-perf Android, deep links, admin flow, fallback states).
 - **Cursor:** The project does not version `.cursor/`. You can mirror this file in `.cursor/rules/` locally; [AGENTS.md](AGENTS.md) is the single versioned reference for AI and maintainers.