fix(desktop): align AI platform sidebar badge with media-account semantics

The AI 平台 badge counted distinct platforms with at least one
active-auth account, while 媒体账号 counted raw account rows
regardless of auth state. The two numbers shared a slot but meant
different things, which made them not comparable at a glance.

Switch the AI 平台 count to mirror 媒体账号: account-level count
of accounts whose platform falls in the monitoring catalog, with
no authState filter.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/desktop-client/src/renderer/components/DesktopShell.vue

@@ -30,9 +30,7 @@ const navItems = computed(() => {
   const data = snapshot.value
   const accounts = data?.accounts ?? []
   const publishIDs = new Set(desktopPublishMediaCatalog.map((item) => item.id))
-  const authorizedMonitoringCount = desktopMonitoringMediaCatalog.filter((platform) =>
-    accounts.find((account) => account.platform === platform.id)?.authState === 'active',
-  ).length
+  const monitoringIDs = new Set(desktopMonitoringMediaCatalog.map((item) => item.id))
 
   return [
     {
@@ -60,7 +58,7 @@ const navItems = computed(() => {
       to: '/ai-platforms',
       title: 'AI 平台',
       description: 'AI 平台一平台一授权，按卡片查看状态与归属',
-      count: authorizedMonitoringCount,
+      count: accounts.filter((item) => monitoringIDs.has(item.platform)).length,
       icon: RobotOutlined,
     },
   ]