fix(pipeline): harden upstream resilience and production shutdown

DoH через DoWithRetry; CDN preview через UpstreamHTTPDo; частичный fail CDN (EVOBGP_CDN_PARTIAL_OK); безопасный доступ к Job.Meta; drain jobs при SIGTERM; ValidateProductionEnforce при EVOBGP_PRODUCTION=1.

Co-authored-by: Cursor <[email protected]>

internal/httpapi/routes_crud.go

@@ -314,7 +314,7 @@ func (s *Server) handlePreviewCDNSource(w http.ResponseWriter, r *http.Request)
 		writeProblem(w, http.StatusUnprocessableEntity, "Unprocessable Entity", "invalid url")
 		return
 	}
-	resp, err := s.cdnHTTP.Do(req)
+	resp, err := pipeline.UpstreamHTTPDo(r.Context(), s.cdnHTTP, req)
 	if err != nil {
 		writeBadGateway(w, "cdn preview fetch", err)
 		return