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/pipeline/refresh.go

@@ -282,7 +282,7 @@ func resolveDomainWithDOHMessage(ctx context.Context, hc *http.Client, baseURL,
 		return nil, err
 	}
 	req.Header.Set("Accept", "application/dns-message")
-	resp, err := hc.Do(req)
+	resp, err := httpclient.DoWithRetry(ctx, hc, req, 3)
 	if err != nil {
 		return nil, err
 	}
@@ -354,7 +354,7 @@ func resolveDomainWithDOHJSON(ctx context.Context, hc *http.Client, baseURL, hos
 	}
 	req.Header.Set("Accept", "application/dns-json")
 
-	resp, err := hc.Do(req)
+	resp, err := httpclient.DoWithRetry(ctx, hc, req, 3)
 	if err != nil {
 		return nil, err
 	}