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-function-length/index.js

@@ -0,0 +1,42 @@
+'use strict';
+
+var GetIntrinsic = require('get-intrinsic');
+var define = require('define-data-property');
+var hasDescriptors = require('has-property-descriptors')();
+var gOPD = require('gopd');
+
+var $TypeError = require('es-errors/type');
+var $floor = GetIntrinsic('%Math.floor%');
+
+/** @type {import('.')} */
+module.exports = function setFunctionLength(fn, length) {
+	if (typeof fn !== 'function') {
+		throw new $TypeError('`fn` is not a function');
+	}
+	if (typeof length !== 'number' || length < 0 || length > 0xFFFFFFFF || $floor(length) !== length) {
+		throw new $TypeError('`length` must be a positive 32-bit integer');
+	}
+
+	var loose = arguments.length > 2 && !!arguments[2];
+
+	var functionLengthIsConfigurable = true;
+	var functionLengthIsWritable = true;
+	if ('length' in fn && gOPD) {
+		var desc = gOPD(fn, 'length');
+		if (desc && !desc.configurable) {
+			functionLengthIsConfigurable = false;
+		}
+		if (desc && !desc.writable) {
+			functionLengthIsWritable = false;
+		}
+	}
+
+	if (functionLengthIsConfigurable || functionLengthIsWritable || !loose) {
+		if (hasDescriptors) {
+			define(/** @type {Parameters<define>[0]} */ (fn), 'length', length, true, true);
+		} else {
+			define(/** @type {Parameters<define>[0]} */ (fn), 'length', length);
+		}
+	}
+	return fn;
+};