fix(desktop): restore managed Node server startup (#348)

## Summary
- revert the Bun standalone desktop packaging path and restore the
server's original `dist/bin.js` bootstrap flow
- add a managed Node runtime for Electron and Tauri that downloads only
the current platform/arch artifact into `~/.config/codenomad`
- update desktop startup and packaging scripts so packaged apps use the
managed runtime consistently, and clean up Electron's expected
navigation-abort log noise

## Testing
- npm run typecheck --workspace @neuralnomads/codenomad-electron-app
- cargo check
- npm run build --workspace @neuralnomads/codenomad
- npm run build:mac --workspace @neuralnomads/codenomad-electron-app
- launch
`packages/electron-app/release/mac-arm64/CodeNomad.app/Contents/MacOS/CodeNomad`
and verify the packaged server reaches ready with the managed Node
runtime

packages/tauri-app/src-tauri/tauri.conf.json

@@ -43,6 +43,11 @@
   "bundle": {
     "active": true,
     "linux": {
+      "appimage": {
+        "files": {
+          "/usr/share/applications/ai.neuralnomads.codenomad.client.desktop": "icons/linux/ai.neuralnomads.codenomad.client.desktop"
+        }
+      },
       "deb": {
         "files": {
           "/usr/share/applications/ai.neuralnomads.codenomad.client.desktop": "icons/linux/ai.neuralnomads.codenomad.client.desktop",