refactor: add service layer architecture with Pydantic validation

- Add services layer (PartyService, ScheduleService, ProductService, ServiceCenterService)
- Add ServiceProvider for dependency injection
- Add Pydantic input validation on all MCP tools
- Add thread-safety to TrytonSettings with double-checked locking
- Update tests to mock ServiceProvider instead of direct client calls
- Add pydantic dependency

pyproject.toml

@@ -8,6 +8,7 @@ dependencies = [
     "fastmcp[tasks]>=3.1.0",
     "sabatron-tryton-rpc-client>=7.4.0",
     "python-dotenv>=1.0.0",
+    "pydantic>=2.0.0",
 ]
 
 [project.optional-dependencies]