build(deps): bump python-json-logger upper bound to <5 (#53)

Widen the version constraint from >=3.2,<4 to >=3.2,<5 to allow
python-json-logger v4.x when it is released. The project uses only
the standard JsonFormatter via Django dictConfig, so none of the v4.0.0
breaking changes (renamed parameters, removed string-based init args)
apply.

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: marevol

backend/pyproject.toml

@@ -31,7 +31,7 @@ dependencies = [
     "channels-redis>=4.2,<5",
     "daphne>=4.1,<5",
     "fastprogress>=1.0.0,<1.1",
-    "python-json-logger>=3.2,<4",
+    "python-json-logger>=3.2,<5",
     "django-celery-beat>=2.7,<3",
 ]