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/__init__.py

@@ -1,5 +1,6 @@
+from .referals import router as referal_router
 from .menus import router as menus_router
 from .support import router as support_router
 from .buy import router as buy_router
 
-routers = [menus_router, support_router, buy_router]
+routers = [referal_router, menus_router, support_router, buy_router]