Load the Network's signing key at start, so /api/ready reports sign-in as it is (it said degraded until the first sign-in)

ddiff --git a/server/index.js b/server/index.js
iindex 277cc17..b39ed49 100644
---- a/server/index.js
++++ b/server/index.js
@@@ -28,6 +28,8 @@ async function start() {
      const { config } = ctx;
      const server = app.listen(config.port, config.host, () => {
          console.log(`[OpenVibe.Design] ${config.nodeEnv} on http://${config.host}:${config.port} → ${config.baseUrl} (network ${config.networkUrl})`);
++        // Load the Network's signing key now, not on the first sign-in, so /api/ready reports sign-in as it is.
++        ctx.keys.ensure().catch(() => {});
      });
      server.keepAliveTimeout = 65_000;
      createLifecycle({ server, ctx });