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/unbox-primitive/test/index.js

@@ -0,0 +1,59 @@
+'use strict';
+
+var test = require('tape');
+var inspect = require('object-inspect');
+var is = require('object-is');
+var forEach = require('for-each');
+var v = require('es-value-fixtures');
+
+var unboxPrimitive = require('..');
+
+test('primitives', function (t) {
+	forEach([null, undefined], function (nullValue) {
+		t['throws'](
+			// @ts-expect-error
+			function () { unboxPrimitive(nullValue); },
+			TypeError,
+			inspect(nullValue) + ' is not a primitive'
+		);
+	});
+
+	// eslint-disable-next-line no-extra-parens
+	forEach(/** @type {typeof v.nonNullPrimitives} */ ([].concat(
+		// @ts-expect-error TS sucks with concat
+		v.nonNullPrimitives,
+		v.zeroes,
+		v.infinities,
+		NaN
+	)), function (primitive) {
+		var obj = Object(primitive);
+		t.ok(
+			is(unboxPrimitive(obj), primitive),
+			inspect(obj) + 'unboxes to ' + inspect(primitive)
+		);
+	});
+
+	t.end();
+});
+
+test('objects', function (t) {
+	// eslint-disable-next-line no-extra-parens
+	forEach(/** @type {typeof v.objects} */ (/** @type {unknown} */ ([].concat(
+		// @ts-expect-error TS sucks with concat
+		v.objects,
+		{},
+		[],
+		function () {},
+		/a/g,
+		new Date()
+	))), function (object) {
+		t['throws'](
+			// @ts-expect-error
+			function () { unboxPrimitive(object); },
+			TypeError,
+			inspect(object) + ' is not a primitive'
+		);
+	});
+
+	t.end();
+});