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/fence.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: "M4 3 2 5v15c0 .6.4 1 1 1h2c.6 0 1-.4 1-1V5Z", key: "1n2rgs" }],
+  ["path", { d: "M6 8h4", key: "utf9t1" }],
+  ["path", { d: "M6 18h4", key: "12yh4b" }],
+  ["path", { d: "m12 3-2 2v15c0 .6.4 1 1 1h2c.6 0 1-.4 1-1V5Z", key: "3ha7mj" }],
+  ["path", { d: "M14 8h4", key: "1r8wg2" }],
+  ["path", { d: "M14 18h4", key: "1t3kbu" }],
+  ["path", { d: "m20 3-2 2v15c0 .6.4 1 1 1h2c.6 0 1-.4 1-1V5Z", key: "dfd4e2" }]
+];
+const Fence = createLucideIcon("fence", __iconNode);
+
+export { __iconNode, Fence as default };
+//# sourceMappingURL=fence.mjs.map