feat(web): 桌面端前端 Web 独立部署适配——浏览器降级桥+登录态引导+页面动态修正

- 新增 web-fallback.ts：无 pywebview 时以浏览器能力降级（文件选择/上传/模板下载/配置），
  其余桌面能力（enqueue_json/vc_*/folder 选择等）保持 undefined 交由页面既有请在本地客户端中打开提示
- 新增 ensure-auth.ts：无 uid 时经 /newApi/check_login 恢复登录态，无 token/失效跳登录页；
  21 个入口 main.ts 挂载前先引导（桌面端已注入 uid 时零开销）
- pywebview.ts：getPywebviewApi() 在纯浏览器环境返回降级桥；新增 isDesktopRuntime 标志
  （首页更新面板/退出链接据此区分桌面与 Web）；hasPywebview 语义修正为真实桥判定
- 登录页跳转、首页登出链接、品牌检测页 hasBridge 判定（select_brand_folder 存在性）适配 Web

frontend-vue/src/pages/home/DesktopHomePage.vue

@@ -4,6 +4,7 @@
       <span class="header-title">数富AI</span>
       <div class="header-right">
         <button
+          v-if="isDesktopRuntime"
           type="button"
           class="header-update-btn"
           title="检测更新"
@@ -25,7 +26,7 @@
           </div>
         </div>
         <span class="username-text">{{ username || '未登录' }}</span>
-        <a href="/logout" class="logout-link">退出</a>
+        <a :href="logoutHref" class="logout-link">退出</a>
       </div>
     </header>
 
@@ -78,6 +79,7 @@
 import { computed, onMounted, ref } from 'vue'
 import { requestGetJson } from '@/shared/api/http'
 import { buildJavaUrl } from '@/shared/api/url'
+import { isDesktopRuntime } from '@/shared/bridges/pywebview'
 import { resolvePageHref } from '@/shared/page-prefix'
 
 const username = ref('')
@@ -88,6 +90,11 @@ const updateReady = ref(false)
 const updateFileUrl = ref('')
 const toastText = ref('')
 
+// 桌面端走 Flask /logout（清 cookie 302 登录页）；Web 独立部署 / dev 跳登录页并清本地 token（login.html?logout=1）
+const logoutHref = computed(() =>
+  isDesktopRuntime.value ? '/logout' : `${resolvePageHref('/new_web_source/login.html')}?logout=1`,
+)
+
 type PermissionState = { amazon: boolean; video: boolean; image: boolean }
 const permissionState = ref<PermissionState>({ amazon: false, video: false, image: false })
 const permissionUnavailable = ref(false)
@@ -95,7 +102,7 @@ const permissionReady = ref(false)
 
 const amazonHref = computed(() => resolvePageHref('/new_web_source/amazon-console.html'))
 const videoHref = computed(() => resolvePageHref('/new_web_source/image-video.html'))
-const imageHref = computed(() => resolvePageHref('/image'))
+const imageHref = computed(() => resolvePageHref('/new_web_source/image.html'))
 
 const canShow = computed(() =>
   permissionUnavailable.value ? { amazon: true, video: true, image: true } : permissionState.value,
@@ -172,7 +179,11 @@ async function loadCurrentUser() {
   try {
     const localName = typeof window === 'undefined' ? '' : window.localStorage.getItem('username') || ''
     if (localName) username.value = localName
-    const resp = await window.fetch('/newApi/check_login', { credentials: 'include' })
+    const token = typeof window === 'undefined' ? '' : window.localStorage.getItem('aiimage_auth_token') || ''
+    const resp = await window.fetch('/newApi/check_login', {
+      credentials: 'include',
+      headers: token ? { Authorization: `Bearer ${token}` } : {},
+    })
     const body = await resp.json().catch(() => ({}))
     if (body?.success && body.data) {
       if (body.data.username) username.value = body.data.username
@@ -257,7 +268,10 @@ async function doUpdate() {
 onMounted(() => {
   void loadCurrentUser()
   void loadPermissions()
-  void fetchVersion().catch(() => undefined)
+  // 版本检测/更新由桌面客户端 Flask 提供，Web 版不发起
+  if (isDesktopRuntime.value) {
+    void fetchVersion().catch(() => undefined)
+  }
 })
 </script>