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>

server/internal/tenant/app/publish_job_service.go

@@ -214,14 +214,16 @@ func (s *PublishJobService) Create(ctx context.Context, actor auth.Actor, req Cr
 
 	for _, task := range createdTasks {
 		if publishErr := publishDesktopTaskEvent(context.Background(), s.messaging, DesktopTaskEvent{
-			Type:           "task_available",
-			TaskID:         task.DesktopID.String(),
-			JobID:          task.JobID.String(),
-			WorkspaceID:    task.WorkspaceID,
-			TargetClientID: task.TargetClientID.String(),
-			Status:         task.Status,
-			Kind:           task.Kind,
-			UpdatedAt:      task.UpdatedAt,
+			Type:            "task_available",
+			TaskID:          task.DesktopID.String(),
+			JobID:           task.JobID.String(),
+			WorkspaceID:     task.WorkspaceID,
+			TargetAccountID: task.TargetAccountID.String(),
+			TargetClientID:  task.TargetClientID.String(),
+			Platform:        task.Platform,
+			Status:          task.Status,
+			Kind:            task.Kind,
+			UpdatedAt:       task.UpdatedAt,
 		}); publishErr != nil {
 			s.logWarn("desktop task available event publish failed", publishErr, zap.String("task_id", task.DesktopID.String()))
 		}