feat: heal dead sync channels and block deleting system default (Z12h)

Ensure default channel and rebind Agent/Binding on list, ticket, agents/me, and ensure-binding so SyncPage does not stay on deleted-channel errors.

Co-authored-by: Cursor <cursoragent@cursor.com>

platform/internal/handler/sync_binding.go

@@ -6,6 +6,7 @@ import (
 
 	"aijianzhan/platform/internal/authx"
 	"aijianzhan/platform/internal/dbsync"
+	"aijianzhan/platform/internal/logic/applogic"
 	"aijianzhan/platform/internal/svc"
 
 	"github.com/zeromicro/go-zero/rest/httpx"
@@ -16,8 +17,11 @@ func syncBindingsListHandler(svcCtx *svc.ServiceContext) http.HandlerFunc {
 		if !requireDBSync(svcCtx, w) {
 			return
 		}
-		localID := r.URL.Query().Get("local_database_id")
 		tid := syncTenantID(r)
+		if _, err := applogic.HealTenantSyncBind(r.Context(), svcCtx, tid); err != nil {
+			_ = err
+		}
+		localID := r.URL.Query().Get("local_database_id")
 		var (
 			list []dbsync.Binding
 			err  error
@@ -74,6 +78,18 @@ func syncBindingsEnsureHandler(svcCtx *svc.ServiceContext) http.HandlerFunc {
 				return
 			}
 		}
+		// Z12h-2：通道空/已删 → 静默挂回公司默认同步
+		needHeal := body.ChannelID == ""
+		if !needHeal {
+			if _, e := svcCtx.DBSync.Store().GetChannelForTenant(body.ChannelID, body.TenantID); e != nil {
+				needHeal = true
+			}
+		}
+		if needHeal {
+			if healed, hErr := applogic.HealTenantSyncBind(r.Context(), svcCtx, body.TenantID); hErr == nil && healed != nil && healed.ChannelID != "" {
+				body.ChannelID = healed.ChannelID
+			}
+		}
 		saved, err := svcCtx.DBSync.Store().EnsureBinding(body)
 		if err != nil {
 			authx.WriteError(w, http.StatusBadRequest, err.Error())