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/monitoring_service.go

@@ -242,17 +242,21 @@ type monitoringConfiguredQuestion struct {
 }
 
 var defaultMonitoringPlatforms = []monitoringPlatformMetadata{
+	{ID: "yuanbao", Name: "混元 / 元宝"},
+	{ID: "kimi", Name: "Kimi"},
+	{ID: "wenxin", Name: "文心一言"},
 	{ID: "deepseek", Name: "DeepSeek"},
-	{ID: "qwen", Name: "通义千问"},
 	{ID: "doubao", Name: "豆包"},
+	{ID: "qwen", Name: "通义千问"},
 }
 
 var monitoringPlatformNames = map[string]string{
 	"deepseek": "DeepSeek",
-	"qwen":     "通义千问",
 	"doubao":   "豆包",
 	"kimi":     "Kimi",
-	"yuanbao":  "腾讯元宝",
+	"qwen":     "通义千问",
+	"wenxin":   "文心一言",
+	"yuanbao":  "混元 / 元宝",
 }
 
 func (s *MonitoringService) DashboardComposite(
@@ -891,7 +895,7 @@ func (s *MonitoringService) ensureCollectNowTasks(
 func (s *MonitoringService) loadQuota(ctx context.Context, tenantID int64) (monitoringQuotaConfig, error) {
 	cfg := monitoringQuotaConfig{
 		CollectionMode:   monitoringCollectorType,
-		EnabledPlatforms: []string{"deepseek", "qwen", "doubao"},
+		EnabledPlatforms: []string{"yuanbao", "kimi", "wenxin", "deepseek", "doubao", "qwen"},
 	}
 
 	var enabledJSON []byte