Add sync error logging, extend error flash, fix unload saves

- Log workforce sync errors to backend stdout so they appear in docker logs
- Extend error flash from 5s to 15s so errors are readable
- Replace sendBeacon (POST-only) with keepalive fetch (PUT) on unload —
  sendBeacon was hitting 404s on all three unload saves

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/node_modules/path-key/index.js

@@ -0,0 +1,16 @@
+'use strict';
+
+const pathKey = (options = {}) => {
+	const environment = options.env || process.env;
+	const platform = options.platform || process.platform;
+
+	if (platform !== 'win32') {
+		return 'PATH';
+	}
+
+	return Object.keys(environment).reverse().find(key => key.toUpperCase() === 'PATH') || 'Path';
+};
+
+module.exports = pathKey;
+// TODO: Remove this for the next major release
+module.exports.default = pathKey;