feat: add database models with cascade delete

Implements SQLAlchemy 2.0 async ORM models (Config, Subscription, ExportLog) with cascade delete-orphan relationships. Upgrades SQLAlchemy to 2.0.49 for Python 3.14 compatibility. Adds pytest conftest with in-memory SQLite fixture; all 4 TDD tests pass.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/models.py

@@ -0,0 +1,66 @@
+from __future__ import annotations
+
+import uuid
+from datetime import datetime
+from typing import Optional
+
+from sqlalchemy import Integer, String, Text, Boolean, DateTime, ForeignKey
+from sqlalchemy.orm import DeclarativeBase, Mapped, mapped_column, relationship
+from sqlalchemy.ext.asyncio import create_async_engine, async_sessionmaker
+
+
+class Base(DeclarativeBase):
+    pass
+
+
+class Config(Base):
+    __tablename__ = "configs"
+
+    id: Mapped[int] = mapped_column(Integer, primary_key=True)
+    name: Mapped[str] = mapped_column(String, nullable=False)
+    token: Mapped[str] = mapped_column(String, unique=True, nullable=False)
+    base_yaml: Mapped[str] = mapped_column(Text, nullable=False)
+    created_at: Mapped[datetime] = mapped_column(DateTime, default=datetime.utcnow)
+    updated_at: Mapped[datetime] = mapped_column(
+        DateTime, default=datetime.utcnow, onupdate=datetime.utcnow
+    )
+
+    subscriptions: Mapped[list["Subscription"]] = relationship(
+        back_populates="config", cascade="all, delete-orphan"
+    )
+    export_logs: Mapped[list["ExportLog"]] = relationship(
+        back_populates="config", cascade="all, delete-orphan"
+    )
+
+
+class Subscription(Base):
+    __tablename__ = "subscriptions"
+
+    id: Mapped[int] = mapped_column(Integer, primary_key=True)
+    config_id: Mapped[int] = mapped_column(Integer, ForeignKey("configs.id"), nullable=False)
+    name: Mapped[str] = mapped_column(String, nullable=False)
+    url: Mapped[str] = mapped_column(String, nullable=False)
+    last_fetched_at: Mapped[Optional[datetime]] = mapped_column(DateTime, nullable=True)
+
+    config: Mapped["Config"] = relationship(back_populates="subscriptions")
+
+
+class ExportLog(Base):
+    __tablename__ = "export_logs"
+
+    id: Mapped[int] = mapped_column(Integer, primary_key=True)
+    config_id: Mapped[int] = mapped_column(Integer, ForeignKey("configs.id"), nullable=False)
+    fetched_at: Mapped[datetime] = mapped_column(DateTime, default=datetime.utcnow)
+    node_count: Mapped[int] = mapped_column(Integer, default=0)
+    success: Mapped[bool] = mapped_column(Boolean, default=True)
+    error_message: Mapped[Optional[str]] = mapped_column(Text, nullable=True)
+
+    config: Mapped["Config"] = relationship(back_populates="export_logs")
+
+
+def make_engine(database_url: str):
+    return create_async_engine(database_url)
+
+
+def make_session_factory(engine):
+    return async_sessionmaker(engine, expire_on_commit=False)