[mod] migrate from Redis to Valkey (#4795)

This patch migrates from `redis==5.2.1` [1] to `valkey==6.1.0` [2].

The migration to valkey is necessary because the company behind Redis has decided
to abandon the open source license. After experiencing a drop in user numbers,
they now want to run it under a dual license again. But this move demonstrates
once again how unreliable the company is and how it treats open source
developers.

To review first, read the docs::

    $ make docs.live

Follow the instructions to remove redis:

- http://0.0.0.0:8000/admin/settings/settings_redis.html

Config and install a local valkey DB:

- http://0.0.0.0:8000/admin/settings/settings_valkey.html

[1] https://pypi.org/project/redis/
[2] https://pypi.org/project/valkey/

Co-authored-by: HLFH <gaspard@dhautefeuille.eu>
Co-authored-by: Markus Heiser <markus.heiser@darmarit.de>

utils/searxng_check.py

@@ -34,8 +34,11 @@ if os.path.isfile(OLD_BRAND_ENV):
     msg = ('%s is no longer needed, remove the file' % (OLD_BRAND_ENV))
     warnings.warn(msg, DeprecationWarning)
 
-from searx import redisdb, get_setting
+from searx import valkeydb, get_setting
 
-if not redisdb.initialize():
-    warnings.warn("can't connect to redis DB at: %s" % get_setting('redis.url'), RuntimeWarning, stacklevel=2)
-    warnings.warn("--> no bot protection without redis DB", RuntimeWarning, stacklevel=2)
+if get_setting('redis.url'):
+    warnings.warn("setting redis.url is deprecated, use valkey.url", RuntimeWarning, stacklevel=2)
+
+if not valkeydb.initialize():
+    warnings.warn("can't connect to valkey DB at: %s" % get_setting('valkey.url'), RuntimeWarning, stacklevel=2)
+    warnings.warn("--> no bot protection without valkey DB", RuntimeWarning, stacklevel=2)