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/logic/applogic/agents.go

@@ -243,6 +243,13 @@ func (l *AuthLogic) IssueClientCredentials(clientID, clientSecret string) (*type
 	if err != nil {
 		return nil, err
 	}
+	if l.svcCtx.DBSync != nil {
+		if _, hErr := HealTenantSyncBind(l.ctx, l.svcCtx, acc.TenantID); hErr == nil {
+			if refreshed, gErr := l.svcCtx.Agents.Get(l.ctx, acc.TenantID, acc.AgentID); gErr == nil && refreshed != nil {
+				acc = refreshed
+			}
+		}
+	}
 	token, exp, err := authx.IssueAgentToken(l.svcCtx.JWT, acc.TenantID, acc.AgentID, acc.Perms)
 	if err != nil {
 		return nil, err