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/is-obj/readme.md

@@ -0,0 +1,34 @@
+# is-obj [![Build Status](https://travis-ci.org/sindresorhus/is-obj.svg?branch=master)](https://travis-ci.org/sindresorhus/is-obj)
+
+> Check if a value is an object
+
+Keep in mind that array, function, regexp, etc, are objects in JavaScript.<br>
+See [`is-plain-obj`](https://github.com/sindresorhus/is-plain-obj) if you want to check for plain objects.
+
+
+## Install
+
+```
+$ npm install --save is-obj
+```
+
+
+## Usage
+
+```js
+const isObj = require('is-obj');
+
+isObj({foo: 'bar'});
+//=> true
+
+isObj([1, 2, 3]);
+//=> true
+
+isObj('foo');
+//=> false
+```
+
+
+## License
+
+MIT © [Sindre Sorhus](https://sindresorhus.com)