set default timeout for pytest (#5265)

Avoid wasting time on broken test that pending the workflow for a long
time like this:
https://github.com/deepmodeling/deepmd-kit/actions/runs/22224311896

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **Chores**
* Added test timeout configuration to prevent indefinitely hanging test
runs, improving test suite reliability and execution stability.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: link89 <3314130+link89@users.noreply.github.com>

Author: link89

pyproject.toml

@@ -88,6 +88,7 @@ test = [
     "pytest-cov",
     "pytest-sugar",
     "pytest-split",
+    "pytest-timeout",
     "dpgui",
     # to support Array API 2024.12
     'array-api-strict>=2.2;python_version>="3.9"',
@@ -464,6 +465,7 @@ runtime-evaluated-base-classes = ["torch.nn.Module"]
 
 [tool.pytest.ini_options]
 markers = "run"
+timeout = 1800
 
 [tool.coverage.run]
 plugins = ["source.3rdparty.coverage_plugins.jit_plugin"]