evert: remove experimental my.dash.board PWA virtual host

Reverts the experimental feature that attempted to serve the dashboard
via a local HTTP server registered as a hardcoded `my.dash.board` virtual
host, intended to satisfy Chrome's PWA "secure origin" installability
requirement. The approach caused proxy connection errors and file-not-found
issues that were not worth resolving.

Removed: native-host/dashboard-server.js, native-host/test-chain.mjs
Reverted: startup.js, message-router.js, virtual-hosts.js, index.js,
          build-distributable.js, extension/pages/virtual-hosts.js,
          CI workflows (ci.yml, release.yml)

native-host/holesail-manager/index.js

@@ -30,7 +30,6 @@ function saveState() {
     id: s.id, port: s.port, host: s.host, secure: s.secure, udp: s.udp || false, label: s.label || ''
   }));
   const virtualHostsList = vhostsModule.getVirtualHosts()
-    .filter(v => v.type !== 'local') // never persist built-in local hosts
     .map(v => ({ hostname: v.hostname, hsUrl: v.hsUrl }));
   const serviceTunnelsList = svcModule.getServiceTunnels().map(t => ({
     id: t.id, label: t.label, hsUrl: t.hsUrl, localPort: t.localPort
@@ -125,7 +124,6 @@ module.exports = {
   getServers: serversModule.getServers,
   // Virtual hosts
   setVirtualHost: vhostsModule.setVirtualHost,
-  setLocalVirtualHost: vhostsModule.setLocalVirtualHost,
   removeVirtualHost: vhostsModule.removeVirtualHost,
   getVirtualHosts: vhostsModule.getVirtualHosts,
   getLocalPortForHostname: vhostsModule.getLocalPortForHostname,