fix: Electron desktop app startup and add install script

- tryElectronApp() now finds the project directory via
  LAZY_UPDATE_MANAGER_DIR env, CWD, binary path, or $HOME
- Launches node_modules/.bin/electron directly instead of npm start
  (avoids recompiling the Go backend on every launch)
- Add install.sh with Electron fallback, desktop launcher, and
  prefer_electron config
- Desktop entry points to electron launcher for wofi support
- Update electron to v41.7.1

package.json

@@ -18,7 +18,7 @@
   "author": "",
   "license": "MIT",
   "devDependencies": {
-    "electron": "^41.5.0",
+    "electron": "^41.7.1",
     "electron-builder": "^26.0.0"
   },
   "build": {