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/book-key.mjs

@@ -0,0 +1,20 @@
+/**
+ * @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: "M13 2H6.5A2.5 2.5 0 0 0 4 4.5v15", key: "4azifu" }],
+  ["path", { d: "M17 2v6", key: "qgmh37" }],
+  ["path", { d: "M17 4h2", key: "13vrzo" }],
+  ["path", { d: "M20 15.2V21a1 1 0 0 1-1 1H6.5a1 1 0 0 1 0-5H20", key: "192hzx" }],
+  ["circle", { cx: "17", cy: "10", r: "2", key: "y0i25j" }]
+];
+const BookKey = createLucideIcon("book-key", __iconNode);
+
+export { __iconNode, BookKey as default };
+//# sourceMappingURL=book-key.mjs.map