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/client/deposit.py

@@ -0,0 +1,58 @@
+from aiogram import F, Router
+from aiogram.fsm.context import FSMContext
+from aiogram.types import CallbackQuery, Message
+
+from bot.keyboards.client import payment_gateways
+from bot.keyboards.common import return_to_menu
+from bot.states.buy import BillingStorage
+from bot.states.deposit import DepositStorage
+from bot.texts import (
+    CHECKOUT_PAYMENT_CHOICE,
+    DEPOSIT_AMOUNT,
+    DEPOSIT_AMOUNT_BELOW_MINIMAL,
+    DEPOSIT_AMOUNT_FALLBACK,
+)
+from config import settings
+from schemas.billing import BillingContext
+from schemas.common import GeneralMessageContext
+
+router = Router()
+
+
+@router.callback_query(F.data == "deposit")
+async def deposit_init(cb: CallbackQuery, state: FSMContext):
+    await state.clear()
+
+    await cb.message.edit_text(DEPOSIT_AMOUNT, reply_markup=return_to_menu)
+
+    ctx = GeneralMessageContext(msg=cb.message)
+    await state.set_state(DepositStorage.amount)
+    await state.set_data({"ctx": ctx})
+
+
+@router.message(DepositStorage.amount)
+async def deposit_amount(msg: Message, state: FSMContext):
+    data = await state.get_data()
+    await state.clear()
+    await msg.delete()
+
+    ctx: GeneralMessageContext | None = data.get("ctx")
+    if not isinstance(ctx, GeneralMessageContext) or not msg.text.isdigit():
+        await msg.answer(DEPOSIT_AMOUNT_FALLBACK, reply_markup=return_to_menu)
+        await state.set_state(DepositStorage.amount)
+        await state.set_data(data)
+        return
+
+    if int(msg.text) < settings.deposit_threshold:
+        await ctx.msg.edit_text(
+            DEPOSIT_AMOUNT_BELOW_MINIMAL.format(threshold=settings.deposit_threshold),
+            reply_markup=return_to_menu,
+        )
+        await state.set_state(DepositStorage.amount)
+        await state.set_data(data)
+        return
+
+    await ctx.msg.edit_text(CHECKOUT_PAYMENT_CHOICE, reply_markup=payment_gateways)
+    await state.set_state(BillingStorage.pending)
+    billing_context = BillingContext(amount=int(msg.text))
+    await state.set_data({"ctx": billing_context})