Issue 1: repo scaffold and project structure

backend/ten31portal/database.py

@@ -0,0 +1,13 @@
+"""Database engine and session management."""
+
+from sqlmodel import Session, create_engine
+
+from ten31portal.config import DB_PATH
+
+engine = create_engine(f"sqlite:///{DB_PATH}", echo=False)
+
+
+def get_session():
+    """FastAPI dependency that yields a database session."""
+    with Session(engine) as session:
+        yield session