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.

docker-compose.yml

@@ -1,14 +1,46 @@
 services:
+  postgres:
+    image: postgres:16-alpine
+    container_name: maleniabot_db
+    environment:
+      POSTGRES_USER: ${POSTGRES_USER:-malenia}
+      POSTGRES_PASSWORD: ${POSTGRES_PASSWORD:-malenia_password}
+      POSTGRES_DB: ${POSTGRES_DB:-malenia_db}
+    volumes:
+      - postgres_data:/var/lib/postgresql/data
+    ports:
+      - "5432:5432"
+    healthcheck:
+      test:
+        [
+          "CMD-SHELL",
+          "pg_isready -U ${POSTGRES_USER:-malenia} -d ${POSTGRES_DB:-malenia_db}",
+        ]
+      interval: 5s
+      timeout: 10s
+      retries: 5
+
   bot:
     build:
-      context: .
       dockerfile: Dockerfile
-    volumes:
-      - .:/app
-    env_file:
-      - .env
+    container_name: maleniabot_app
+    depends_on:
+      postgres:
+        condition: service_healthy
+    environment:
+      BOT_TOKEN: ${BOT_TOKEN}
+      POSTGRES_URL: postgresql+asyncpg://${POSTGRES_USER:-malenia}:${POSTGRES_PASSWORD:-malenia_password}@postgres:5432/${POSTGRES_DB:-malenia_db}
+      PROXY: ${PROXY:-}
+      ADMIN_GROUP_ID: ${ADMIN_GROUP_ID}
+      REMNAWAVE_URL: ${REMNAWAVE_URL}
+      SUBSCRIPTION_URL: ${SUBSCRIPTION_URL}
+      REMNAWAVE_TOKEN: ${REMNAWAVE_TOKEN}
+      MIN_DEVICES: ${MIN_DEVICES:-3}
+      MAX_DEVICES: ${MAX_DEVICES:-12}
+      PER_DEVICE_COST: ${PER_DEVICE_COST:-50}
+      WHITELIST_COST: ${WHITELIST_COST:-100}
+      WHITELIST_DEVICE_THRESHOLD: ${WHITELIST_DEVICE_THRESHOLD:-6}
     restart: unless-stopped
-    # Optional: uncomment to run with auto-reload for development
-    # command: python -m watchfiles main.py
-    stdin_open: true
-    tty: true
+
+volumes:
+  postgres_data: