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/hash.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 = [
+  ["line", { x1: "4", x2: "20", y1: "9", y2: "9", key: "4lhtct" }],
+  ["line", { x1: "4", x2: "20", y1: "15", y2: "15", key: "vyu0kd" }],
+  ["line", { x1: "10", x2: "8", y1: "3", y2: "21", key: "1ggp8o" }],
+  ["line", { x1: "16", x2: "14", y1: "3", y2: "21", key: "weycgp" }]
+];
+const Hash = createLucideIcon("hash", __iconNode);
+
+export { __iconNode, Hash as default };
+//# sourceMappingURL=hash.mjs.map