Refactor bot handlers and keyboards; implement admin features

- Removed unused prehandling, referrals, support, and states files.
- Updated admin and client handlers to improve structure and functionality.
- Introduced admin filters and routers for better access control.
- Added new billing and deposit functionalities for client interactions.
- Enhanced keyboard layouts for admin and client menus.
- Implemented promotion handling for admin users.
- Updated configuration to include admin settings.
- Improved utility functions for quote fetching and menu text building.
- Added common handlers for undefined commands and message deletions.

bot/handlers/admins/admins.py

@@ -0,0 +1,36 @@
+from aiogram import F, Router
+from aiogram.filters import Command
+from aiogram.fsm.context import FSMContext
+from aiogram.types import CallbackQuery, Message
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from bot.filters.admins import AdminFilter
+from bot.keyboards.admins import main_menu
+from misc.utils import build_adm_main_menu_text
+from schemas.di import DependenciesDTO
+
+router = Router()
+
+
+@router.message(AdminFilter(), Command(commands=["start", "cancel"]))
+async def standard_start(
+    msg: Message, state: FSMContext, session: AsyncSession, deps: DependenciesDTO
+):
+    await state.clear()
+
+    users = await deps.user_repository.user_count(session)
+    await msg.answer(
+        build_adm_main_menu_text(user_count=users, user_id=msg.from_user.id), reply_markup=main_menu
+    )
+
+
+@router.callback_query(AdminFilter(), F.data == "menu:main")
+async def main_menu_cb(
+    cb: CallbackQuery, state: FSMContext, session: AsyncSession, deps: DependenciesDTO
+):
+    await state.clear()
+
+    users = await deps.user_repository.user_count(session)
+    await cb.message.edit_text(
+        build_adm_main_menu_text(user_count=users, user_id=cb.from_user.id), reply_markup=main_menu
+    )