Fix CI for Django 6 on Python 3.9-3.11

Author: Copilot

requirements.txt

@@ -1,7 +1,8 @@
 requests~=2.32.5; python_version < "3.10"
 requests~=2.34.0; python_version >= "3.10"
 # Core dependencies
-django>=6.0.6,<6.1.0
+django>=4.2.0,<5.0.0; python_version < "3.12"
+django>=6.0.6,<6.1.0; python_version >= "3.12"
 python-dotenv>=1.0.0
 cryptography>=46.0.6,<47.0
 pyjwt>=2.10.0