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/set-proto/test/index.js

@@ -0,0 +1,40 @@
+'use strict';
+
+var test = require('tape');
+
+var setProto = require('../');
+
+var isPrototypeOf = Object.prototype.isPrototypeOf;
+
+test('setProto', function (t) {
+	t.equal(typeof setProto, 'function', 'is a function');
+
+	t.test('can set', { skip: !setProto }, function (st) {
+		var obj = { a: 1 };
+		var proto = { b: 2 };
+
+		st.ok(isPrototypeOf.call(Object.prototype, obj), 'Object.prototype is isPrototypeOf obj');
+		st.notOk(isPrototypeOf.call(proto, obj), 'proto is not isPrototypeOf obj');
+		st.ok('a' in obj, 'a is in obj');
+		st.notOk('b' in obj, 'b is not in obj');
+
+		// eslint-disable-next-line no-extra-parens
+		st.equal(/** @type {NonNullable<typeof setProto>} */ (setProto)(obj, proto), obj, 'returns the object');
+
+		st.ok(isPrototypeOf.call(Object.prototype, obj), 'Object.prototype is isPrototypeOf obj');
+		st.ok(isPrototypeOf.call(proto, obj), 'proto is isPrototypeOf obj');
+		st.ok('a' in obj, 'a is in obj');
+		st.ok('b' in obj, 'b is in obj');
+
+		st.equal(Object.getPrototypeOf(obj), proto, 'sets the prototype');
+		st.end();
+	});
+
+	t.test('can not set', { skip: !!setProto }, function (st) {
+		st.equal(setProto, null);
+
+		st.end();
+	});
+
+	t.end();
+});