feat: add admin promotion broadcast system and psql health check

- Add `/push` command for admins to broadcast messages to all users
  with approve/decline confirmation flow (handlers/ads.py)
- Add common handler for undefined commands and delete callback
- Add `UserRepository.get_users()` to fetch all users
- Add `UserService.send_promotion_to_users()` with error logging
- Add promotion confirmation keyboard and FSM state
- Add PostgreSQL availability check in startup.sh before migrations
- Add new text constants for promotion flow

handlers/__init__.py

@@ -1,6 +1,8 @@
+from .ads import router as ads_router
 from .buy import router as buy_router
+from .common import router as common_router
 from .menus import router as menus_router
 from .referals import router as referal_router
 from .support import router as support_router
 
-routers = [referal_router, menus_router, support_router, buy_router]
+routers = [referal_router, menus_router, ads_router, support_router, buy_router, common_router]