chore: migrate to svelte 5

src/routes/+layout.svelte

@@ -1,8 +1,15 @@
 <script>
   import "../app.css";
+  /**
+   * @typedef {Object} Props
+   * @property {import('svelte').Snippet} [children]
+   */
+
+  /** @type {Props} */
+  let { children } = $props();
 </script>
 
 <header class="fixed z-50 mix-blend-difference p-1">
   <a href="/" class="text-white text-2xl">schreifuchs.ch</a>
 </header>
-<slot />
+{@render children?.()}