Fix mounted event after initial hydration (#3480)

* trigger queued mounted events immediately after hydrating

* add a playwright test to prevent regressions

packages/playwright-tests/fullstack-mounted/src/main.rs

@@ -0,0 +1,23 @@
+// Regression test for https://github.com/DioxusLabs/dioxus/pull/3480
+
+use dioxus::prelude::*;
+
+fn main() {
+    dioxus::launch(App);
+}
+
+#[component]
+fn App() -> Element {
+    let mut mounted = use_signal(|| false);
+
+    rsx! {
+        div {
+            onmounted: move |_| {
+                mounted.set(true);
+            },
+            if mounted() {
+                "The mounted event was triggered."
+            }
+        }
+    }
+}