feat: add pytest testing infrastructure

- Add test optional dependencies to pyproject.toml
- Add conftest.py with fixtures for mocking settings and MCP client
- Add test_server.py with tests for tryton_call and MCP tools

pyproject.toml

@@ -10,6 +10,13 @@ dependencies = [
     "python-dotenv>=1.0.0",
 ]
 
+[project.optional-dependencies]
+test = [
+    "pytest>=8.0.0",
+    "pytest-mock>=3.14.0",
+    "pytest-asyncio>=0.25.0",
+]
+
 [tool.setuptools.packages.find]
 where = ["src"]
 include = ["*"]