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/support.py

@@ -53,7 +53,6 @@ async def received_message(
     F.from_user.is_bot == False,  # noqa: E712
     ~Command("close"),
     ~Command("refpay"),
-    F.text,
 )
 async def handle_admin_message(
     msg: Message, state: FSMContext, session: AsyncSession, deps: DependenciesDTO