Increment 1 server side. Move livekitToken() into server/livekit.js (shared by routes.js
and calls.js). calls.js now mints a per-callee LiveKit join token and calls.js/push.js
put {livekitUrl, livekitToken} in the VoIP invite payload, so the native plugin can
connect the LiveKit room immediately on answer — even from a killed state, before the
WebView loads. No behaviour change while CALLKIT_ENABLED=0.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
