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.

.gitignore

@@ -8,6 +8,7 @@
 /dist
 .DS_Store
 /examples/assets/test_video.mp4
+/examples/_assets/test_video.mp4
 static
 
 # new recommendation to keep the lockfile in for CI and reproducible builds