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.

misc/utils.py

@@ -1,3 +1,4 @@
+import urllib.parse
 from typing import Optional
 from random import choice
 from datetime import datetime, timedelta, timezone
@@ -175,10 +176,15 @@ def format_subscription_link(link: Optional[str] = None):
     return f"<code>{link or '...'}</code>"
 
 
+def format_share_deep_link(link: str):
+    return f"https://t.me/share/url/?url={urllib.parse.quote_plus(link)}"
+
+
 def format_support_subscription(
     subscription: SubscriptionPlan,
     full_name: str,
     user_id: int,
+    balance: int,
     username: Optional[str] = None,
 ) -> str:
     username = format_username(username)
@@ -196,6 +202,7 @@ def format_support_subscription(
         devices=subscription.devices,
         whitelist_description=whitelist_description,
         price=calculate_price(subscription),
+        balance=balance,
     )