fix: resolve Windows compilation errors and warnings

- Add Manager trait import for windows_startup_cmd.rs
- Add explicit type annotations for PathBuf in windows_startup_cmd.rs
- Fix unused import warning in screenshot_capture_service.rs
- Prefix unused variables with underscore in runner.rs and aster_agent_cmd.rs
- Update package.json with Node.js engine requirement

docs/package.json

@@ -1,5 +1,8 @@
 {
   "name": "proxycast-docs",
+  "engines": {
+    "node": ">=22.0.0"
+  },
   "scripts": {
     "dev": "nuxt dev --extends docus",
     "build": "nuxt build --extends docus",