build(deps): bump authlib from 1.6.9 to 1.6.12

Bumps [authlib](https://github.com/authlib/authlib) from 1.6.9 to 1.6.12.
- [Release notes](https://github.com/authlib/authlib/releases)
- [Changelog](https://github.com/authlib/authlib/blob/1.6.12/docs/changelog.rst)
- [Commits](authlib/authlib@v1.6.9...1.6.12)

---
updated-dependencies:
- dependency-name: authlib
  dependency-version: 1.6.12
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

pyproject.toml

@@ -40,7 +40,7 @@ dependencies = [
   "annotated-types==0.7.0",
   "anyio==4.9.0",
   "attrs==25.3.0",
-  "Authlib==1.6.9",
+  "Authlib==1.6.12",
   "certifi==2025.6.15",
   "cffi==2.0.0",
   "charset-normalizer==3.4.2",