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/get-proto/index.js

@@ -0,0 +1,27 @@
+'use strict';
+
+var reflectGetProto = require('./Reflect.getPrototypeOf');
+var originalGetProto = require('./Object.getPrototypeOf');
+
+var getDunderProto = require('dunder-proto/get');
+
+/** @type {import('.')} */
+module.exports = reflectGetProto
+	? function getProto(O) {
+		// @ts-expect-error TS can't narrow inside a closure, for some reason
+		return reflectGetProto(O);
+	}
+	: originalGetProto
+		? function getProto(O) {
+			if (!O || (typeof O !== 'object' && typeof O !== 'function')) {
+				throw new TypeError('getProto: not an object');
+			}
+			// @ts-expect-error TS can't narrow inside a closure, for some reason
+			return originalGetProto(O);
+		}
+		: getDunderProto
+			? function getProto(O) {
+				// @ts-expect-error TS can't narrow inside a closure, for some reason
+				return getDunderProto(O);
+			}
+			: null;