feat: add FastAPI app factory and health check endpoint

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

tests/conftest.py

@@ -0,0 +1,28 @@
+"""Shared test fixtures for the SneakySwole test suite."""
+
+import os
+from unittest.mock import patch
+
+import pytest
+from fastapi.testclient import TestClient
+
+
+@pytest.fixture(autouse=True)
+def _set_test_env() -> None:
+    """Ensure required env vars are set for all tests."""
+    with patch.dict(os.environ, {
+        "ADMIN_USERNAME": "testadmin",
+        "ADMIN_PASSWORD": "testpass123",
+        "APP_ENV": "development",
+        "DATABASE_URL": "sqlite:///data/test_sneakyswole.db",
+    }, clear=False):
+        yield
+
+
+@pytest.fixture
+def client() -> TestClient:
+    """Create a FastAPI TestClient for integration tests."""
+    from app.main import create_app
+
+    app = create_app()
+    return TestClient(app)