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/mouse-left.mjs

@@ -0,0 +1,18 @@
+/**
+ * @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: "M12 7.318V10", key: "17s7lh" }],
+  ["path", { d: "M5 10v5a7 7 0 0 0 14 0V9c0-3.527-2.608-6.515-6-7", key: "imk5ea" }],
+  ["circle", { cx: "7", cy: "4", r: "2", key: "ra7k3" }]
+];
+const MouseLeft = createLucideIcon("mouse-left", __iconNode);
+
+export { __iconNode, MouseLeft as default };
+//# sourceMappingURL=mouse-left.mjs.map