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/unicode-canonical-property-names-ecmascript/README.md

@@ -0,0 +1,58 @@
+# unicode-canonical-property-names-ecmascript [![unicode-canonical-property-names-ecmascript on npm](https://img.shields.io/npm/v/unicode-canonical-property-names-ecmascript)](https://www.npmjs.com/package/unicode-canonical-property-names-ecmascript)
+
+_unicode-canonical-property-names-ecmascript_ exports the set of canonical Unicode property names that are supported in [ECMAScript RegExp property escapes](https://github.com/tc39/proposal-regexp-unicode-property-escapes).
+
+## Installation
+
+To use _unicode-canonical-property-names-ecmascript_, install it as a dependency via [npm](https://www.npmjs.com/):
+
+```bash
+$ npm install unicode-canonical-property-names-ecmascript
+```
+
+Then, `require` it:
+
+```js
+const properties = require('unicode-canonical-property-names-ecmascript');
+```
+
+## Example
+
+```js
+properties.has('ID_Start');
+// → true
+properties.has('IDS');
+// → false
+```
+
+## For maintainers
+
+### How to publish a new release
+
+1. On the `main` branch, bump the version number in `package.json`:
+
+    ```sh
+    npm version patch -m 'Release v%s'
+    ```
+
+    Instead of `patch`, use `minor` or `major` [as needed](https://semver.org/).
+
+    Note that this produces a Git commit + tag.
+
+1. Push the release commit and tag:
+
+    ```sh
+    git push && git push --tags
+    ```
+
+    Our CI then automatically publishes the new release to npm.
+
+## Author
+
+| [![twitter/mathias](https://gravatar.com/avatar/24e08a9ea84deb17ae121074d0f17125?s=70)](https://twitter.com/mathias "Follow @mathias on Twitter") |
+|---|
+| [Mathias Bynens](https://mathiasbynens.be/) |
+
+## License
+
+_unicode-canonical-property-names-ecmascript_ is available under the [MIT](https://mths.be/mit) license.