feat: add subscription and transaction repositories

- Implemented SubscriptionRepository with methods to get, create, and update subscriptions.
- Added BalanceTXRepository for creating and retrieving balance transactions.
- Introduced a test script for simulating Pally webhook for local testing.

db/models/subscriptions.py

@@ -0,0 +1,35 @@
+from datetime import datetime
+from typing import TYPE_CHECKING
+
+from sqlalchemy import BOOLEAN, INTEGER, Boolean, DateTime, Enum, ForeignKey
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from db.base import Base
+from schemas.subscriptions import SubscriptionStatus
+
+if TYPE_CHECKING:
+    from db.models.users import User
+
+
+class Subscription(Base):
+    __tablename__ = "subscriptions"
+
+    user_id: Mapped[int] = mapped_column(ForeignKey("users.id"), primary_key=True)
+    end_date: Mapped[datetime] = mapped_column(DateTime(timezone=True), nullable=False)
+    autorenew: Mapped[bool] = mapped_column(Boolean, default=False)
+    status: Mapped[SubscriptionStatus] = mapped_column(
+        Enum(
+            SubscriptionStatus,
+            name="subscriptionstatus",
+            values_callable=lambda x: [e.value for e in x],
+        ),
+        default=SubscriptionStatus.EXPIRED,
+    )
+
+    devices: Mapped[int] = mapped_column(INTEGER, nullable=False, default=3)
+    whitelists: Mapped[bool] = mapped_column(BOOLEAN, nullable=False, default=False)
+
+    plan_price_paid: Mapped[int] = mapped_column(INTEGER, nullable=False, default=0)
+    duration_days: Mapped[int] = mapped_column(INTEGER, nullable=False, default=30)
+
+    user: Mapped["User"] = relationship(back_populates="subscription")