refactor: 拆分 App.vue 为独立组件，修复多项敷衍方案

- 提取 TitleBar、Sidebar、RoamDrawer、CloseModal 四个组件
- App.vue 从 676 行精简至 238 行，职责更清晰
- 修复评论点赞无限+1：改为基于服务端 liked 字段切换
- 修复评论点赞无防重复：添加 likingSet 锁
- 修复评论点赞用本地缓存：likedIds 改为从服务端 likelist API 同步
- 删除 likedIds 写 localStorage 的 watch
- 播放失败/FM加载失败/减少推荐失败添加 showToast 用户提示
- 抽屉遮罩下标题栏按钮保持原色（z-10 提升至遮罩之上）

src/components/TitleBar.vue

@@ -0,0 +1,43 @@
+<template>
+  <div
+    data-tauri-drag-region
+    class="h-10 flex items-center justify-between px-4 flex-shrink-0 select-none relative z-10"
+    :class="darkMode ? '' : 'bg-surface/90 backdrop-blur'"
+  >
+    <slot name="left">
+      <span v-if="!darkMode" class="text-xs text-content-3 font-medium ml-2">Nekosonic Music</span>
+    </slot>
+    <div class="flex items-center gap-1.5">
+      <button @click="minimizeWindow" class="w-3 h-3 rounded-full bg-yellow-500 hover:bg-yellow-400 transition" title="最小化"></button>
+      <button @click="toggleMaximize" class="w-3 h-3 rounded-full bg-green-500 hover:bg-green-400 transition" title="最大化/还原"></button>
+      <button @click="$emit('close')" class="w-3 h-3 rounded-full bg-red-500 hover:bg-red-400 transition" title="关闭"></button>
+    </div>
+  </div>
+</template>
+
+<script setup lang="ts">
+import { getCurrentWindow } from '@tauri-apps/api/window';
+
+defineProps<{
+  darkMode?: boolean;
+}>();
+
+defineEmits<{
+  close: [];
+}>();
+
+const currentWindow = getCurrentWindow();
+
+function minimizeWindow() {
+  currentWindow.minimize();
+}
+
+async function toggleMaximize() {
+  const isMaximized = await currentWindow.isMaximized();
+  if (isMaximized) {
+    currentWindow.unmaximize();
+  } else {
+    currentWindow.maximize();
+  }
+}
+</script>