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-front-tunnel.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 22V12a10 10 0 1 1 20 0v10", key: "o0fyp0" }],
+  ["path", { d: "M15 6.8v1.4a3 2.8 0 1 1-6 0V6.8", key: "m8q3n9" }],
+  ["path", { d: "M10 15h.01", key: "44in9x" }],
+  ["path", { d: "M14 15h.01", key: "5mohn5" }],
+  ["path", { d: "M10 19a4 4 0 0 1-4-4v-3a6 6 0 1 1 12 0v3a4 4 0 0 1-4 4Z", key: "hckbmu" }],
+  ["path", { d: "m9 19-2 3", key: "iij7hm" }],
+  ["path", { d: "m15 19 2 3", key: "npx8sa" }]
+];
+const TrainFrontTunnel = createLucideIcon("train-front-tunnel", __iconNode);
+
+export { __iconNode, TrainFrontTunnel as default };
+//# sourceMappingURL=train-front-tunnel.mjs.map