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/07-fullstack/hello-world/src/main.rs

@@ -0,0 +1,59 @@
+//! A simple hello world example for Dioxus fullstack
+//!
+//! Run with:
+//!
+//! ```sh
+//! dx serve --web
+//! ```
+//!
+//! This example demonstrates a simple Dioxus fullstack application with a client-side counter
+//! and a server function that returns a greeting message.
+//!
+//! The `use_action` hook makes it easy to call async work (like server functions) from the client side
+//! and handle loading and error states.
+
+use dioxus::prelude::*;
+use dioxus_fullstack::get;
+
+fn main() {
+    dioxus::launch(app);
+}
+
+fn app() -> Element {
+    let mut count = use_signal(|| 0);
+    let mut message = use_action(get_greeting);
+
+    rsx! {
+        div { style: "padding: 2rem; font-family: Arial, sans-serif;",
+            h1 { "Hello, Dioxus Fullstack!" }
+
+            // Client-side counter - you can use any client functionality in your app!
+            div { style: "margin: 1rem 0;",
+                h2 { "Client Counter: {count}" }
+                button { onclick: move |_| count += 1, "Increment" }
+                button { onclick: move |_| count -= 1, "Decrement" }
+            }
+
+            // We can handle the action result and display loading state
+            div { style: "margin: 1rem 0;",
+                h2 { "Server Greeting" }
+                button { onclick: move |_| message.call("World".to_string(), 30), "Get Server Greeting" }
+                if message.is_pending() {
+                    p { "Loading..." }
+                }
+                p { "{message:#?}" }
+            }
+        }
+    }
+}
+
+/// A simple server function that returns a greeting
+///
+/// Our server function takes a name as a path and query parameters as inputs and returns a greeting message.
+#[get("/api/greeting/{name}/{age}")]
+async fn get_greeting(name: String, age: i32) -> Result<String> {
+    Ok(format!(
+        "Hello from the server, {}! You are {} years old. 🚀",
+        name, age
+    ))
+}