The per-client app registered its redirect URI under the `web` platform,
so Entra treated it as a confidential client and the connect token
exchange (PKCE, no secret) failed with AADSTS7000218 (client_secret
required). Register the redirect under `publicClient` instead — matching
the desktop reference (PublicClient.RedirectUris) — so the secretless
PKCE code redemption is accepted.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>