Added pytest configuration and first 4 unit tests

pytest.ini

@@ -0,0 +1,19 @@
+[pytest]
+testpaths = tests
+python_files = test_*.py
+python_functions = test_*
+asyncio_mode = auto
+filterwarnings =
+    ignore::DeprecationWarning:botocore.auth
+
+# Coverage configuration
+addopts =
+    --cov=app
+    --cov-report=term-missing
+
+# Test markers
+markers =
+    slow: mark tests as slow running
+    integration: integration tests
+    unit: unit tests
+    db: tests requiring database