Web UI: enable VNC over websockets

This issue likely involves multiple parts:
- [x] Build [`websockify`](https://github.com/novnc/websockify) for putting a proxy between QEMU and the browser; this is required to "translate" VNC from QEMU to websockets, which allows connections from the websocket client on the browser.
- [ ] Setup self-signed certificate for `wss://` (secured).
- [x] ~~Enable clients from outside the subnet (firewall) to use VNC; this likely involves Apache `ws_tunnel`.~~ No longer relevant because Apache has been replaced with the `nodejs` server.
- [x] ~Create mechanism to auto-generate token/passphrase for connection (as a temporary solution).~ Unnecessary for now because there are already 2 layers of authentication: 1) log in to the web UI, and 2) log in to the server VM.