调整按钮逻辑，减少闪动

src/components/MainpageButton.svelte

@@ -2,8 +2,15 @@
   import { onMount } from 'svelte'
   import { mainpageClick, mainpageGetClick } from '../lib/apis/legacy/mainpage'
 
-  let clicks = 0
-  let clicksPending = 0
+  interface Props {
+    initialClicks?: number
+  }
+
+  let { initialClicks = 0 }: Props = $props()
+
+  // svelte-ignore state_referenced_locally
+  let clicks = $state(initialClicks)
+  let clicksPending = $state(0)
 
   onMount(() => {
     // 先 fetch 一次