[fix] harmonize default settings for caching of /static files

Caching files on the client side for more than a day can confuse the end user
when updating static files[1].

Depending on the way of providing a SearXNG instance via HTTP, there are several
ways to optimize the access to the /static files.  However, since we don't know
what optimization an admin has provided for his static files, we should have
moderate settings in the defaults that run robustly in a wide variety of
installations.

In this sense, all caches on the client side should be cleared after one day at
the latest.  So far the files were cached for one year on client side; as soon
as changes are made to the static files (with the option `static_use_hash:
true`) the old static files are kept for one year on the CLient side / which can
also be evaluated as unnecessary caching.

[1] https://github.com/searxng/searxng/discussions/2821



Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>