重构：Wails v3 迁移 + 前端目录规范化 + Sidebar滚动优化

- web/ → frontend/ 目录重命名（Wails v3 标准结构）
- main.go: Middleware 修复 custom.js 404 + DevTools 延迟启动
- Sidebar: 收藏夹内部独立滚动 + 帮助区块固定底部
- useFavorites.ts: longPressTimer const→let 修复 TypeError
- App.vue: Arco Tabs padding-top 覆盖
- build: config.yml / Taskfile.yml 对齐官方模板，devtools build tag
- 新增 v3 bindings、vite.config.js、跨平台构建配置

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

build/android/app/src/main/res/values/themes.xml

@@ -0,0 +1,14 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <style name="Theme.WailsApp" parent="Theme.MaterialComponents.DayNight.NoActionBar">
+        <!-- Primary brand color. -->
+        <item name="colorPrimary">@color/wails_blue</item>
+        <item name="colorPrimaryVariant">@color/wails_blue_dark</item>
+        <item name="colorOnPrimary">@android:color/white</item>
+        <!-- Status bar color. -->
+        <item name="android:statusBarColor">@color/wails_background</item>
+        <item name="android:navigationBarColor">@color/wails_background</item>
+        <!-- Window background -->
+        <item name="android:windowBackground">@color/wails_background</item>
+    </style>
+</resources>