chore(project): add PyPI status badges to README and modernize pyproject.toml metadata

- Add PyPI version and Python versions badges to README.md header
- Update pyproject.toml license declaration to PEP 621 format: license = { text = "BSD-3-Clause" }
- Remove deprecated license-files from [tool.setuptools] section (now handled at top level)
- Remove redundant "License :: OSI Approved :: BSD License" classifier

Author: pangpang20

README.md

@@ -1,4 +1,7 @@
 # GaussDB dialect for Django
+![PyPI](https://img.shields.io/pypi/v/gaussdb-django)
+![PyPI - Python Version](https://img.shields.io/pypi/pyversions/gaussdb-django)
+
 
 This adds compatibility for [GaussDB](https://github.com/HuaweiCloudDeveloper/gaussdb-django) to Django.
 

pyproject.toml

@@ -8,12 +8,12 @@ version = "4.2.0"
 description = "Django backend for GaussDB"
 readme = "README.md"
 requires-python = ">=3.10"
-license = "BSD-3-Clause"
+license = { text = "BSD-3-Clause" }
+license-files = ["LICENSE"]
 classifiers = [
   "Development Status :: 5 - Production/Stable",
   "Framework :: Django",
   "Framework :: Django :: 4.2",
-  "License :: OSI Approved :: BSD License",
   "Operating System :: OS Independent",
   "Programming Language :: Python",
   "Programming Language :: Python :: 3",
@@ -30,4 +30,3 @@ vector = ["numpy~=1.0"]
 
 [tool.setuptools]
 packages = ["gaussdb_django"]
-license-files = ["LICENSE"]