✅(summary) add minimal test suite for health endpoint

Based on cameldev's work, introduce basic tests to ensure the
health endpoint responds correctly.

src/summary/pyproject.toml

@@ -21,8 +21,16 @@ dependencies = [
 [project.optional-dependencies]
 dev = [
     "ruff==0.14.4",
+    "pytest==9.0.2",
+    "responses>=0.25.8",
 ]
 
+[tool.pytest.ini_options]
+markers = [
+    "api: Test the API",
+]
+testpaths = ["tests"]
+
 [build-system]
 requires = ["setuptools>=61.0"]
 build-backend = "setuptools.build_meta"
@@ -49,6 +57,7 @@ select = [
     "T20", # flake8-print
     "W",  # pycodestyle warning
 ]
+ignore= ["PLR2004"]
 
 [tool.ruff.lint.per-file-ignores]
 "tests/*" = [