fix(httpclient): replace DefaultClient with timed clients and retry

Пакет httpclient: timeout 45s, idle pool, DoWithRetry. Scheduler и nodecli
используют retry; pipeline/asnresolve/jobs — httpclient.New вместо DefaultClient.

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

internal/httpclient/httpclient_test.go

@@ -0,0 +1,39 @@
+package httpclient
+
+import (
+	"context"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+	"time"
+)
+
+func TestDoWithRetry_retriesOn500(t *testing.T) {
+	var calls int
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		calls++
+		if calls < 3 {
+			http.Error(w, "fail", http.StatusBadGateway)
+			return
+		}
+		w.WriteHeader(http.StatusOK)
+		_, _ = w.Write([]byte("ok"))
+	}))
+	defer srv.Close()
+
+	req, err := http.NewRequest(http.MethodGet, srv.URL, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	resp, err := DoWithRetry(context.Background(), New(5*time.Second), req, 3)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer func() { _ = resp.Body.Close() }()
+	if resp.StatusCode != http.StatusOK {
+		t.Fatalf("status %d", resp.StatusCode)
+	}
+	if calls != 3 {
+		t.Fatalf("want 3 calls, got %d", calls)
+	}
+}