[Code scan] Package metadata allows incompatible Pydantic 1 installations

This issue was found by a Codex global repository scan of tracked non-test files at commit `8c93925cb10b401b2b83c738bd9263fd74474468`.

### Relevant code
https://github.com/deepmodeling/LAMBench/blob/8c93925cb10b401b2b83c738bd9263fd74474468/pyproject.toml#L8-L19
https://github.com/deepmodeling/LAMBench/blob/8c93925cb10b401b2b83c738bd9263fd74474468/lambench/models/basemodel.py#L1-L22
https://github.com/deepmodeling/LAMBench/blob/8c93925cb10b401b2b83c738bd9263fd74474468/lambench/metrics/post_process.py#L180-L190

### Impact
The dependency is declared as bare `pydantic`, but the code uses Pydantic 2 APIs such as `ConfigDict` and `model_dump()`. A resolver can legally install Pydantic 1 when another package constrains it, which would make imports or runtime calls fail.

### Suggested fix
Declare the intended major version explicitly, for example `pydantic>=2,<3`, or remove Pydantic 2-only APIs if Pydantic 1 compatibility is intended.