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/train-track.mjs

@@ -0,0 +1,22 @@
+/**
+ * @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: "M2 17 17 2", key: "18b09t" }],
+  ["path", { d: "m2 14 8 8", key: "1gv9hu" }],
+  ["path", { d: "m5 11 8 8", key: "189pqp" }],
+  ["path", { d: "m8 8 8 8", key: "1imecy" }],
+  ["path", { d: "m11 5 8 8", key: "ummqn6" }],
+  ["path", { d: "m14 2 8 8", key: "1vk7dn" }],
+  ["path", { d: "M7 22 22 7", key: "15mb1i" }]
+];
+const TrainTrack = createLucideIcon("train-track", __iconNode);
+
+export { __iconNode, TrainTrack as default };
+//# sourceMappingURL=train-track.mjs.map