Enable TLS for UI and API

[jescalada]

Is your feature request related to a problem? Please describe.
Currently, TLS is configurable only for the proxy. We could extend the implementation to add secure connections to the API/UI server.

The current implementation allows configuring the TLS parameters as follows (config.schema.json):

"tls": {
  "description": "TLS configuration for secure connections",
  "type": "object",
  "properties": {
    "enabled": { "type": "boolean" },
    "key": { "type": "string" },
    "cert": { "type": "string" }
  },
  "required": ["enabled", "key", "cert"]
},

These values are fetched and used when creating the server:

if (getTLSEnabled()) {
  await new Promise<void>((resolve, reject) => {
    const server = https.createServer(getServerOptions(), this.expressApp!);
    server.on('error', reject);
    server.listen(proxyHttpsPort, () => {
      console.log(`HTTPS Proxy Listening on ${proxyHttpsPort}`);
      resolve();
    });
    this.httpsServer = server;
  });
}

Describe the solution you'd like
It would be nice to extend this implementation so that the API/UI server can make use of TLS as well.

Additional context
#1391 (comment)