refactor(svelte5): rewrite useRemember for Svelte 5

Replaces the Svelte 3/4 store-based useRemember implementation with a Svelte 5 composable using $state and $effect. Removes Svelte store and lifecycle dependencies to align with Svelte 5 patterns.

Author: brodienguyen

packages/svelte5/src/useRemember.svelte.ts

@@ -0,0 +1,12 @@
+import { router } from '@inertiajs/core'
+
+export default function useRemember<State extends object>(initialState: State, key?: string): State {
+  const restored = router.restore(key) as State | undefined
+  const state = $state(restored !== undefined ? restored : initialState)
+
+  $effect(() => {
+    router.remember(state, key)
+  })
+
+  return state
+}