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

repositories/users.py

@@ -6,6 +6,12 @@ from schemas.users import NewUserDTO
 
 
 class UserRepository:
+    async def get_users(self, session: AsyncSession) -> list[User]:
+        stmt = select(User)
+        res = await session.execute(stmt)
+
+        return list(res.scalars().all())
+
     async def get_user_by_id(self, session: AsyncSession, user_id: int) -> User | None:
         stmt = select(User).where(User.id == user_id)
         result = await session.execute(stmt)