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-alert.mjs

@@ -0,0 +1,24 @@
+/**
+ * @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: "M12 13h.01", key: "y0uutt" }],
+  ["path", { d: "M12 6v3", key: "1m4b9j" }],
+  [
+    "path",
+    {
+      d: "M4 19.5v-15A2.5 2.5 0 0 1 6.5 2H19a1 1 0 0 1 1 1v18a1 1 0 0 1-1 1H6.5a1 1 0 0 1 0-5H20",
+      key: "k3hazp"
+    }
+  ]
+];
+const BookAlert = createLucideIcon("book-alert", __iconNode);
+
+export { __iconNode, BookAlert as default };
+//# sourceMappingURL=book-alert.mjs.map