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/desktop_task_events.go

@@ -9,14 +9,16 @@ import (
 )
 
 type DesktopTaskEvent struct {
-	Type           string    `json:"type"`
-	TaskID         string    `json:"task_id"`
-	JobID          string    `json:"job_id"`
-	WorkspaceID    int64     `json:"workspace_id"`
-	TargetClientID string    `json:"target_client_id"`
-	Status         string    `json:"status"`
-	Kind           string    `json:"kind"`
-	UpdatedAt      time.Time `json:"updated_at"`
+	Type            string    `json:"type"`
+	TaskID          string    `json:"task_id"`
+	JobID           string    `json:"job_id"`
+	WorkspaceID     int64     `json:"workspace_id"`
+	TargetAccountID string    `json:"target_account_id"`
+	TargetClientID  string    `json:"target_client_id"`
+	Platform        string    `json:"platform"`
+	Status          string    `json:"status"`
+	Kind            string    `json:"kind"`
+	UpdatedAt       time.Time `json:"updated_at"`
 }
 
 func publishDesktopTaskEvent(ctx context.Context, client *rabbitmq.Client, event DesktopTaskEvent) error {