exam chronological ordering

[mostafam99]

modified sort_key function to adjust slightly for exam months. the values are small so they don't conflict with year ordering. i don't know if this is a good fix or not

[yutotakano]

Thanks for the PR! I like the 0.1/0.2/0.3/0.4 idea, but I'm not sure I like adding hardcoded values to these sort keys. I found an interesting function in the Python standard library that maybe we can use, could you look into that?

[yutotakano]

Thanks a lot for working through this! Been bugging many people I think, your help is much appreciated.

[yutotakano]

There was a regression introduced by this PR where visiting the FNLP page would crash the backend:

2026-01-23T19:38:51.100 INFO [gunicorn] [ERROR] Internal Server Error: /api/category/listexams/fnlp/
2026-01-23T19:38:51.101 INFO [gunicorn] Traceback (most recent call last):
2026-01-23T19:38:51.101 INFO [gunicorn]   File "/usr/local/lib/python3.9/dist-packages/django/core/handlers/exception.py", line 56, in inner
2026-01-23T19:38:51.101 INFO [gunicorn]     response = get_response(request)
2026-01-23T19:38:51.101 INFO [gunicorn]   File "/usr/local/lib/python3.9/dist-packages/django/core/handlers/base.py", line 197, in _get_response
2026-01-23T19:38:51.101 INFO [gunicorn]     response = wrapped_callback(request, *callback_args, **callback_kwargs)
2026-01-23T19:38:51.101 INFO [gunicorn]   File "/app/util/response.py", line 34, in wrapper
2026-01-23T19:38:51.101 INFO [gunicorn]     return f(request, *args, **kwargs)
2026-01-23T19:38:51.101 INFO [gunicorn]   File "/app/ediauth/auth_check.py", line 86, in wrapper
2026-01-23T19:38:51.101 INFO [gunicorn]     return f(request, *args, **kwargs)
2026-01-23T19:38:51.101 INFO [gunicorn]   File "/app/categories/views.py", line 119, in list_exams
2026-01-23T19:38:51.101 INFO [gunicorn]     res = sorted(
2026-01-23T19:38:51.102 INFO [gunicorn] TypeError: '<' not supported between instances of 'tuple' and 'datetime.datetime'

Fixed in #74.