Use LogWarning instead of LogError for handled OAuth failures

OAuth failures like timeout and invitation-required are expected
conditions that are already displayed in the status text. Using
LogError triggers SimpleErrorHandler to show an exception popup,
which is redundant and distracting.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/main/csharp/net/eagle0/clients/unity/eagle0/Assets/Auth/OAuthManager.cs

@@ -158,7 +158,7 @@ namespace Auth {
                 // Bring game back to foreground even on failure
                 WindowFocusManager.BringToForeground();
 
-                Debug.LogError($"[OAuthManager] Login failed: {ex.Message}");
+                Debug.LogWarning($"[OAuthManager] Login failed: {ex.Message}");
                 OnLoginFailed?.Invoke(ex.Message);
                 throw;
             }

src/main/csharp/net/eagle0/clients/unity/eagle0/Assets/ConnectionHandler/ConnectionHandler.cs

@@ -499,7 +499,7 @@ public class ConnectionHandler : MonoBehaviour, ILobbySubscriber, IDisposable {
             await OAuthManager.Instance.LoginAsync(provider);
             // OnLoginSuccess or OnNewUserNeedsDisplayName will be called
         } catch (Exception ex) {
-            Debug.LogError($"OAuth login failed: {ex.Message}");
+            Debug.LogWarning($"OAuth login failed: {ex.Message}");
             if (oauthStatusText != null) { oauthStatusText.text = $"Login failed: {ex.Message}"; }
         }
     }