feat: add database engine and session management

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

tests/test_database.py

@@ -0,0 +1,26 @@
+"""Tests for database engine and session management."""
+
+from sqlmodel import Session
+
+from app.database import get_engine, get_db_session
+
+
+class TestDatabase:
+    """Tests for database connection management."""
+
+    def test_get_engine_returns_engine(self) -> None:
+        """get_engine should return a SQLAlchemy engine instance."""
+        engine = get_engine("sqlite:///data/test.db")
+        assert engine is not None
+        assert "sqlite" in str(engine.url)
+
+    def test_get_db_session_yields_session(self) -> None:
+        """get_db_session should yield a usable SQLModel Session."""
+        engine = get_engine("sqlite:///:memory:")
+        session_gen = get_db_session(engine)
+        session = next(session_gen)
+        assert isinstance(session, Session)
+        try:
+            next(session_gen)
+        except StopIteration:
+            pass