do not use set_defaults for architecture arguments

according to the source code defaults always updates the values
dictionary. This in this specific case it is impossible to override the
value it will be always empty list.

In order to handle it we are adding another property to the Handler
class which allows to run with None architecture list.

This particular set_defaults behaviour is still useful for other cases
when we have to run command without any specific architecture

src/ahriman/application/handlers/web.py

@@ -31,6 +31,7 @@ class Web(Handler):
     web server handler
     """
 
+    ALLOW_AUTO_ARCHITECTURE_RUN = False
     ALLOW_MULTI_ARCHITECTURE_RUN = False  # required to be able to spawn external processes
 
     @classmethod