feat: add ManualDNSChallenge component and related hooks for manual DNS challenge management

- Implemented `useManualChallenge`, `useChallengePoll`, and `useManualChallengeMutations` hooks for managing manual DNS challenges.
- Created tests for the `useManualChallenge` hooks to ensure correct fetching and mutation behavior.
- Added `ManualDNSChallenge` component for displaying challenge details and actions.
- Developed end-to-end tests for the Manual DNS Provider feature, covering provider selection, challenge UI, and accessibility compliance.
- Included error handling tests for verification failures and network errors.

backend/internal/utils/url_testing_enhanced_test.go

@@ -112,7 +112,7 @@ func TestTestURLConnectivity_RedirectValidation(t *testing.T) {
 	// Create test servers
 	privateServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		w.WriteHeader(http.StatusOK)
-		w.Write([]byte("Private server"))
+		_, _ = w.Write([]byte("Private server"))
 	}))
 	defer privateServer.Close()