feat(pwa): experimental — add my.dash.board virtual host for secure PWA install

Serve the dashboard over a local HTTPS virtual host (my.dash.board) so
Chrome treats it as a secure origin and shows the PWA install prompt.

- Add native-host/dashboard-server.js: bare-http1 static file server
  backed by bare-bundle assets in distribution mode, disk fallback in dev
- Add setLocalVirtualHost() to virtual-hosts.js; type:local entries are
  protected from removal and filtered out of saveState persistence
- Export setLocalVirtualHost from holesail-manager/index.js
- Start dashboard server in startup.js after proxies are ready and
  register my.dash.board as a local virtual host
- Stop dashboard server in message-router.js cleanup()
- Update manifest.webmanifest: start_url, id, scope → https://my.dash.board/
- Embed all extension/dashboard/ files as bare-bundle assets in
  build-distributable.js patchBundle() — no installer copy step needed
- Hide checkbox, hs:// URL, Reconnect, and Remove controls for built-in
  my.dash.board row in the virtual hosts table UI

extension/dashboard/manifest.webmanifest

@@ -1,10 +1,10 @@
 {
-  "id": "/dashboard/dashboard.html",
+  "id": "https://my.dash.board/",
   "name": "Holesail Browser",
   "short_name": "Holesail",
   "description": "P2P Holesail tunnels in the browser",
-  "start_url": "dashboard.html",
-  "scope": ".",
+  "start_url": "https://my.dash.board/",
+  "scope": "https://my.dash.board/",
   "display": "standalone",
   "display_override": ["window-controls-overlay", "standalone"],
   "background_color": "#0f1117",
@@ -12,7 +12,7 @@
   "protocol_handlers": [
     {
       "protocol": "web+holesail",
-      "url": "dashboard.html?lookup=%s"
+      "url": "https://my.dash.board/?lookup=%s"
     }
   ],
   "screenshots": [