chore: drop Python 3.11 support

Remove Python 3.11 from CI matrix and package classifiers.
Python 3.12 is now the minimum supported version.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: feanil

.github/workflows/ci.yml

@@ -14,7 +14,7 @@ jobs:
     strategy:
       matrix:
         os: [ ubuntu-latest ]
-        python-version: ['3.11', '3.12']
+        python-version: ['3.12']
         toxenv: [quality, docs, django42-drf315, django42-drflatest, django52-drf315, django52-drflatest]
 
     steps:

setup.py

@@ -143,7 +143,6 @@ def get_version(*file_paths):
         'Operating System :: OS Independent',
         'Programming Language :: Python',
         'Programming Language :: Python :: 3',
-        'Programming Language :: Python :: 3.11',
         'Programming Language :: Python :: 3.12',
     ],
     packages=find_packages(include=['submissions*'], exclude=['*.test', '*.tests']),