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/table-of-contents.mjs

@@ -0,0 +1,21 @@
+/**
+ * @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: "M16 5H3", key: "m91uny" }],
+  ["path", { d: "M16 12H3", key: "1a2rj7" }],
+  ["path", { d: "M16 19H3", key: "zzsher" }],
+  ["path", { d: "M21 5h.01", key: "wa75ra" }],
+  ["path", { d: "M21 12h.01", key: "msek7k" }],
+  ["path", { d: "M21 19h.01", key: "qvbq2j" }]
+];
+const TableOfContents = createLucideIcon("table-of-contents", __iconNode);
+
+export { __iconNode, TableOfContents as default };
+//# sourceMappingURL=table-of-contents.mjs.map