feat: add SQLAlchemy database layer with get_db dependency

app/core/database.py

@@ -0,0 +1,22 @@
+from sqlalchemy import create_engine
+from sqlalchemy.orm import DeclarativeBase, Session, sessionmaker
+
+from app.core.config import get_settings
+
+settings = get_settings()
+
+_connect_args = {"check_same_thread": False} if settings.DATABASE_URL.startswith("sqlite") else {}
+engine = create_engine(settings.DATABASE_URL, connect_args=_connect_args)
+SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
+
+
+class Base(DeclarativeBase):
+    pass
+
+
+def get_db() -> Session:
+    db = SessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()

tests/test_database.py

@@ -0,0 +1,16 @@
+from sqlalchemy.orm import Session
+from app.core.database import Base, get_db
+
+
+def test_get_db_yields_session():
+    gen = get_db()
+    db = next(gen)
+    assert isinstance(db, Session)
+    try:
+        next(gen)
+    except StopIteration:
+        pass
+
+
+def test_base_has_metadata():
+    assert Base.metadata is not None