* fix(fullstack-macro): allow server functions to be called without HTTP context
Server functions can now be invoked directly from server-side code without
requiring an HTTP request context. When called outside an HTTP handler,
extractors will use default values instead of failing, matching the behavior
of the old server_fn implementation.
Closes#4907
* fix(fullstack-macro): allow server functions without extractors to be called from backend
Functions with no server extractors use Default::default() and work from backend code.
Functions with extractors still require HTTP context.
Closes#4907