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>

frontend/vite.config.js

@@ -0,0 +1,46 @@
+import { defineConfig } from 'vite'
+import vue from '@vitejs/plugin-vue'
+import { resolve } from 'path'
+import { fileURLToPath } from 'url'
+import AutoImport from 'unplugin-auto-import/vite'
+import Components from 'unplugin-vue-components/vite'
+import { ArcoResolver } from 'unplugin-vue-components/resolvers'
+
+export default defineConfig({
+  plugins: [
+    vue(),
+    AutoImport({
+      imports: ['vue'],
+      dts: 'src/auto-imports.d.ts',
+    }),
+    Components({
+      resolvers: [ArcoResolver({ sideEffect: true })],
+      dts: 'src/components.d.ts',
+    })
+  ],
+  resolve: {
+    alias: {
+      '@': resolve(__dirname, 'src'),
+      '@wailsio/events': fileURLToPath(new URL('./node_modules/@wailsio/runtime/dist/events.js', import.meta.url))
+    }
+  },
+  build: {
+    outDir: 'dist',
+    emptyOutDir: true,
+    sourcemap: false,
+    minify: 'esbuild',
+    cssCodeSplit: true,
+    chunkSizeWarningLimit: 1000,
+    target: 'es2020',
+    rollupOptions: {
+      output: {
+        chunkFileNames: 'assets/js/[name]-[hash].js',
+        entryFileNames: 'assets/js/[name]-[hash].js',
+        assetFileNames: 'assets/[ext]/[name]-[hash].[ext]'
+      }
+    }
+  },
+  optimizeDeps: {
+    include: ['vue', 'pinia', '@arco-design/web-vue', 'marked', 'highlight.js']
+  }
+})