feat(monitoring): decouple AI platforms from media_platforms and expand catalog to 6

Add ai_platforms table + shared catalog (yuanbao/kimi/wenxin/deepseek/doubao/qwen),
drop FKs from platform_accounts and desktop_tasks to media_platforms, and wire
target_account_id + platform into DesktopTaskEvent so the desktop runtime no
longer has to infer them from local state. Desktop client gains generic AI page
detection for binding, drops stale-business-date monitor tasks at the edge, and
refactors AccountsView/AiPlatformsView around the shared catalog. Admin tracking
view surfaces per-platform sampling status cards.

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

apps/desktop-client/src/renderer/lib/client-errors.ts

@@ -42,7 +42,7 @@ function presentClientError(kind: ClientActionKind, error: unknown): ClientError
       ? "账号绑定失败"
       : kind === "unbind-account"
         ? "账号解绑失败"
-        : "打开创作台失败",
+        : "打开平台失败",
   );
 
   if (message === "desktop_account_bind_window_closed") {
@@ -77,7 +77,7 @@ function presentClientError(kind: ClientActionKind, error: unknown): ClientError
     };
   }
 
-  if (message.startsWith("desktop_publish_platform_not_supported:")) {
+  if (message.startsWith("desktop_platform_not_supported:")) {
     const platformId = message.split(":")[1] || "当前平台";
     return {
       tone: "error",
@@ -105,7 +105,7 @@ function presentClientError(kind: ClientActionKind, error: unknown): ClientError
   if (kind === "open-console") {
     return {
       tone: "error",
-      title: "打开创作台失败",
+      title: "打开平台失败",
       content: message,
     };
   }