fix: use select account prompt for sso oidc (#2065)

Use the `select_account` prompt for SSO OIDC to avoid constantly asking
for credentials to be entered with a client has an existing session with
the SSO provider.

packages/auth/server/routes/oauth.ts

@@ -50,5 +50,6 @@ export const oauthRoute = new Hono<HonoAuthContext>()
     return await handleOAuthAuthorizeUrl({
       c,
       clientOptions,
+      prompt: 'select_account',
     });
   });