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/cone.mjs

@@ -0,0 +1,17 @@
+/**
+ * @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: "m20.9 18.55-8-15.98a1 1 0 0 0-1.8 0l-8 15.98", key: "53pte7" }],
+  ["ellipse", { cx: "12", cy: "19", rx: "9", ry: "3", key: "1ji25f" }]
+];
+const Cone = createLucideIcon("cone", __iconNode);
+
+export { __iconNode, Cone as default };
+//# sourceMappingURL=cone.mjs.map