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.

examples/10-integrations/native-headless-in-bevy/README.md

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+Example: Integrating Dioxus into a Bevy application
+
+This example demonstrates rendering a Dioxus application onto a texture within a Bevy application.
+
+## Core Concepts
+- Render a headless Dioxus-native app to a texture.
+- Share and display the texture on a quad in the Bevy app.
+- Transmit mouse and keyboard events from Bevy to Dioxus.
+  - Events are captured when hovering over elements with the `catch-events` class, ensuring only Dioxus receives them.
+- Manage application state through channel messages between Dioxus and Bevy.
+