Add referral system and user balance tracking

Introduce balance field to User model with Alembic migration. Add
referral menu, admin /refpay command, and deep link sharing. Update
Dockerfile to multi-stage build and add Postgres service to compose.
Fix deep link parsing logic and conditional proxy initialization.

handlers/referals.py

@@ -0,0 +1,63 @@
+from aiogram import Router, F
+from aiogram.filters import Command, CommandObject
+from aiogram.utils.deep_linking import create_start_link
+from aiogram.types import CallbackQuery, Message
+from aiogram.fsm.context import FSMContext
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from keyboards.client import referals_kb
+from misc.utils import format_share_deep_link
+from schemas.di import DependenciesDTO
+from texts import GENERAL_PROCESSING, REFERALS_MENU
+from config import settings
+
+router = Router()
+
+
+@router.callback_query(F.data == "referal")
+async def referal_menu(
+    cb: CallbackQuery, state: FSMContext, session: AsyncSession, deps: DependenciesDTO
+):
+    await state.clear()
+
+    user = await deps.user_repository.get_user_by_id(session, cb.from_user.id)
+    referal_link = await create_start_link(cb.bot, f"ref_{user.id}", encode=True)
+    share_link = format_share_deep_link(referal_link)
+
+    await cb.message.edit_text(
+        REFERALS_MENU.format(balance=user.balance, link=referal_link),
+        reply_markup=referals_kb(share_link),
+    )
+
+
+@router.message(F.chat.id == settings.admin_group_id, Command("refpay"))
+async def refpay(
+    msg: Message,
+    command: CommandObject,
+    state: FSMContext,
+    session: AsyncSession,
+    deps: DependenciesDTO,
+):
+    await state.clear()
+
+    await msg.delete()
+    status_msg = await msg.answer(GENERAL_PROCESSING)
+    user = await deps.user_service.fetch_user_by_thread(session, msg.message_thread_id)
+    referal = await deps.user_repository.get_user_by_id(session, user.referal_id)
+    if not referal:
+        await status_msg.edit_text("❌ У пользователя нет реферала.")
+        return
+
+    amount = command.args
+
+    if not amount.isdigit():
+        await status_msg.edit_text(
+            "❌ Укажите в аргументах количество средств, которые необходимо перевести рефералу пользователя."
+        )
+        return
+
+    amount = int(amount)
+    await deps.user_repository.increase_user_balance(session, user.id, amount)
+    await status_msg.edit_text(
+        f"<b>💸 Баланс реферала ({referal.id}) пополнен на {amount}₽</b>"
+    )