fix(account): preserve runtime state during credentials-only updates

backend/internal/service/account_credentials_persistence.go

@@ -0,0 +1,30 @@
+package service
+
+import "context"
+
+type accountCredentialsUpdater interface {
+	UpdateCredentials(ctx context.Context, id int64, credentials map[string]any) error
+}
+
+func persistAccountCredentials(ctx context.Context, repo AccountRepository, account *Account, credentials map[string]any) error {
+	if repo == nil || account == nil {
+		return nil
+	}
+
+	account.Credentials = cloneCredentials(credentials)
+	if updater, ok := any(repo).(accountCredentialsUpdater); ok {
+		return updater.UpdateCredentials(ctx, account.ID, account.Credentials)
+	}
+	return repo.Update(ctx, account)
+}
+
+func cloneCredentials(in map[string]any) map[string]any {
+	if in == nil {
+		return map[string]any{}
+	}
+	out := make(map[string]any, len(in))
+	for k, v := range in {
+		out[k] = v
+	}
+	return out
+}