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/01-app-demos/hotdog/src/backend.rs

@@ -0,0 +1,41 @@
+use anyhow::Result;
+use dioxus::prelude::*;
+
+#[cfg(feature = "server")]
+thread_local! {
+    static DB: std::sync::LazyLock<rusqlite::Connection> = std::sync::LazyLock::new(|| {
+        let conn = rusqlite::Connection::open("hotdogdb/hotdog.db").expect("Failed to open database");
+
+        conn.execute_batch(
+            "CREATE TABLE IF NOT EXISTS dogs (
+                id INTEGER PRIMARY KEY,
+                url TEXT NOT NULL
+            );",
+        )
+        .unwrap();
+
+        conn
+    });
+}
+
+#[get("/api/dogs")]
+pub async fn list_dogs() -> Result<Vec<(usize, String)>> {
+    DB.with(|db| {
+        Ok(db
+            .prepare("SELECT id, url FROM dogs ORDER BY id DESC LIMIT 10")?
+            .query_map([], |row| Ok((row.get(0)?, row.get(1)?)))?
+            .collect::<Result<Vec<(usize, String)>, rusqlite::Error>>()?)
+    })
+}
+
+#[delete("/api/dogs/{id}")]
+pub async fn remove_dog(id: usize) -> Result<()> {
+    DB.with(|db| db.execute("DELETE FROM dogs WHERE id = ?1", [id]))?;
+    Ok(())
+}
+
+#[post("/api/dogs")]
+pub async fn save_dog(image: String) -> Result<()> {
+    DB.with(|db| db.execute("INSERT INTO dogs (url) VALUES (?1)", [&image]))?;
+    Ok(())
+}