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/lucide-react/dist/esm/icons/monitor-smartphone.mjs

@@ -0,0 +1,19 @@
+/**
+ * @license lucide-react v1.24.0 - ISC
+ *
+ * This source code is licensed under the ISC license.
+ * See the LICENSE file in the root directory of this source tree.
+ */
+
+import createLucideIcon from '../createLucideIcon.mjs';
+
+const __iconNode = [
+  ["path", { d: "M18 8V6a2 2 0 0 0-2-2H4a2 2 0 0 0-2 2v7a2 2 0 0 0 2 2h8", key: "10dyio" }],
+  ["path", { d: "M10 19v-3.96 3.15", key: "1irgej" }],
+  ["path", { d: "M7 19h5", key: "qswx4l" }],
+  ["rect", { width: "6", height: "10", x: "16", y: "12", rx: "2", key: "1egngj" }]
+];
+const MonitorSmartphone = createLucideIcon("monitor-smartphone", __iconNode);
+
+export { __iconNode, MonitorSmartphone as default };
+//# sourceMappingURL=monitor-smartphone.mjs.map