add splash screen

src/splash/App.vue

@@ -0,0 +1,44 @@
+<script setup lang="ts">
+import { onMounted, ref } from 'vue'
+import { invoke } from '@tauri-apps/api/core'
+import { Loader2, DownloadCloud, CheckCircle2, AlertCircle } from 'lucide-vue-next'
+
+const status = ref('正在初始化...')
+const isError = ref(false)
+
+onMounted(async () => {
+    try {
+        status.value = '正在检查运行环境...'
+        // This command checks and downloads binaries if missing
+        await invoke('init_ytdlp')
+        
+        status.value = '准备就绪'
+        setTimeout(async () => {
+             await invoke('close_splash')
+        }, 800)
+    } catch (e: any) {
+        status.value = '启动错误: ' + (e.toString() || '未知错误')
+        isError.value = true
+    }
+})
+</script>
+
+<template>
+    <div class="h-screen w-screen bg-white dark:bg-zinc-900 flex flex-col items-center justify-center select-none cursor-default p-8 text-center overflow-hidden" data-tauri-drag-region>
+        <div class="mb-6 relative w-20 h-20 bg-blue-600 rounded-2xl shadow-xl flex items-center justify-center text-white">
+             <DownloadCloud v-if="!isError" class="w-10 h-10" />
+             <AlertCircle v-else class="w-10 h-10" />
+        </div>
+        
+        <h1 class="text-xl font-bold text-zinc-900 dark:text-white mb-6">流萤 - 视频下载</h1>
+        
+        <div class="flex flex-col items-center gap-3 w-full max-w-xs">
+            <div class="flex items-center gap-2.5 text-sm font-medium transition-colors duration-300"
+                 :class="isError ? 'text-red-500' : 'text-gray-600 dark:text-gray-300'">
+                <Loader2 v-if="!isError && status !== '准备就绪'" class="animate-spin w-4 h-4" />
+                <CheckCircle2 v-if="status === '准备就绪'" class="w-4 h-4 text-green-500" />
+                <span>{{ status }}</span>
+            </div>
+        </div>
+    </div>
+</template>