feat(online-inbox): gate access on Zitadel "user" project role

The Online API now requires the "user" project role (claim
urn:zitadel:iam:org:project:roles) instead of an ALLOWED_USER_IDS allowlist.

- IOnlineAuthProvider: add GetAccessTokenAsync(forceRefresh) overload
- ZitadelAuthProvider: forceRefresh drops the cached token and re-runs the
  refresh-token grant to mint a fresh, role-bearing token
- OnlineInboxApiClient: on 401, force-refresh and retry once; if still 401,
  throw a clear "missing 'user' role" error
- OnlineSyncService: surface the 401 at Error level (no longer silent)
- UI: ZitadelTokenInspector decodes the access token after login and warns
  early when the "user" role is absent (fail-open); shown in settings
- docs: online-inbox-api-contract reflects role-based access (no allowlist)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/ClaudeDo.Ui/Services/OnlineLoginService.cs

@@ -34,7 +34,13 @@ public sealed class OnlineLoginService : IOnlineLoginService
                 return new OnlineLoginResult(false, null,
                     "No refresh token returned. Ensure 'offline_access' is in scope and the client allows it.");
 
-            return new OnlineLoginResult(true, result.RefreshToken, null);
+            // Early heads-up: if the access token lacks the "user" project role the server will
+            // reject sync with a 401. Login still succeeds; surface this as a warning, not an error.
+            var warning = ZitadelTokenInspector.HasUserRole(result.AccessToken)
+                ? null
+                : "missing-user-role";
+
+            return new OnlineLoginResult(true, result.RefreshToken, null, warning);
         }
         catch (OperationCanceledException)
         {