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.

.gitignore

@@ -130,6 +130,7 @@ celerybeat.pid
 
 # Environments
 .env
+dev.env
 .venv
 env/
 venv/
@@ -172,7 +173,4 @@ cython_debug/
 .ruff_cache/
 
 # PyPI configuration file
-.pypirc
-
-# Static / IMG
-static/img
+.pypirc