codify "platform" into resolution logic, server-fn/fullstack overhaul (#4596)

overhaul dioxus fullstack using a new implementation of server_fn

This PR is a complete rewrite of dioxus fullstack designed to improve compatibility with axum and to fix a number of compilation errors based on feature flag unification plumbing through macros.

.github/actions/free-disk-space/action.yml

@@ -12,3 +12,6 @@ runs:
       sudo rm -rf /usr/share/dotnet
       sudo rm -rf /usr/local/lib/android
       sudo rm -rf /usr/share/swift
+      sudo docker image prune --all --force || true
+
+