Initial commit: BARON SSO 샘플 (WebView OIDC PKCE 인증 라이브러리 + 데모 앱)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

BaronSoftware.SSO/OIDC/TokenResponse.cs

@@ -0,0 +1,10 @@
+namespace BaronSoftware.SSO
+{
+    /// <summary>토큰 엔드포인트 응답.</summary>
+    internal sealed record TokenResponse(
+        string IdToken,
+        string AccessToken,
+        string? RefreshToken,
+        int ExpiresIn,
+        string RawJson);
+}