Add FastAPI backend with agent system

backend/app/models/test_folder.py

@@ -0,0 +1,8 @@
+import pytest
+from app.models.folder import Folder
+
+
+def test_folder_model_creation():
+    folder = Folder(user_id="test-user", name="Test Folder")
+    assert folder.name == "Test Folder"
+    assert folder.parent_id is None