feat(workspace): replace supported platform count with bound media account count

The "platforms" stat tile was a constant (5) that never reflected what the
tenant actually had set up. Drop SupportedPlatformCount from the workspace
overview API/domain/shared-types and have admin-web compute a bound media
account count from the desktop accounts list, filtered through a new
isMediaPublishAccount helper that excludes deleted rows and AI-only
platforms (yuanbao/kimi/wenxin/deepseek/doubao/qwen).

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

apps/admin-web/src/views/MediaView.vue

@@ -8,7 +8,7 @@ import { useI18n } from "vue-i18n";
 import { mediaApi, resolveApiURL, tenantAccountsApi } from "@/lib/api";
 import { resolveAccountCheckedAt, resolveAccountHealth } from "@/lib/desktop-account-runtime";
 import { formatDateTime } from "@/lib/display";
-import { getPublishPlatformMeta, isPublishPlatformId, normalizePublishPlatformId } from "@/lib/publish-platforms";
+import { getPublishPlatformMeta, isMediaPublishAccount, normalizePublishPlatformId } from "@/lib/publish-platforms";
 
 type AccountHealthFilter = "all" | "live" | "captcha" | "risk" | "expired";
 type PublishState = "immediate" | "queued" | "unavailable";
@@ -79,8 +79,7 @@ const platformMap = computed(() => {
 
 const mediaAccounts = computed<MediaAccountCard[]>(() => {
   return [...(accountsQuery.data.value ?? [])]
-    .filter((account) => !account.deleted_at)
-    .filter((account) => isPublishPlatformId(account.platform))
+    .filter(isMediaPublishAccount)
     .map((account) => {
       const platformId = normalizePublishPlatformId(account.platform);
       const platform = platformMap.value.get(platformId);