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/workflows/promote.yml

@@ -22,7 +22,7 @@ permissions:
 
 jobs:
   promote:
-    runs-on: ubuntu-latest
+    runs-on: blacksmith-4vcpu-ubuntu-2404
     steps:
       - uses: actions/checkout@v5
       - name: Publish the next pre-release