build(pyproject): adopt PEP 639 license metadata (#964)

Problem
- Several packages still use deprecated table-based `project.license`
metadata.
- PEP 639 standardizes SPDX `license` plus `license-files`.

Change
- Replace deprecated `project.license = {file/text = ...}` with an SPDX
expression.
- Add `project.license-files`.
- Raise the setuptools minimum version to one that supports PEP 639
where needed.
- Remove legacy `License ::` classifiers superseded by the SPDX
expression.

Notes
- This change is metadata-only and does not alter runtime behavior.

Authored by OpenClaw (model: gpt-5.4)


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

## Summary by CodeRabbit

* **Chores**
  * Updated build system requirements (setuptools ≥77.0.3)
  * Clarified project license declaration to LGPL-3.0-or-later

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

Author: njzjz-bot

pyproject.toml

@@ -1,5 +1,5 @@
 [build-system]
-requires = ["setuptools>=61", "setuptools_scm[toml]>=7"]
+requires = ["setuptools>=77.0.3", "setuptools_scm[toml]>=7"]
 build-backend = "setuptools.build_meta"
 
 [project]
@@ -10,13 +10,13 @@ authors = [
   {name = "DeepModeling"},
   {name = "Han Wang", email = "wang_han@iapcm.ac.cn"},
 ]
-license = {file = "LICENSE"}
+license = "LGPL-3.0-or-later"
+license-files = ["LICENSE"]
 classifiers = [
     "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",
     "Programming Language :: Python :: 3.12",
     "Programming Language :: Python :: 3.13",
-    "License :: OSI Approved :: GNU Lesser General Public License v3 (LGPLv3)",
 ]
 dependencies = [
     'numpy>=1.14.3',