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/bell-dot.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: "M10.268 21a2 2 0 0 0 3.464 0", key: "vwvbt9" }],
+  [
+    "path",
+    {
+      d: "M11.68 2.009A6 6 0 0 0 6 8c0 4.499-1.411 5.956-2.738 7.326A1 1 0 0 0 4 17h16a1 1 0 0 0 .74-1.673c-.824-.85-1.678-1.731-2.21-3.348",
+      key: "xaq59h"
+    }
+  ],
+  ["circle", { cx: "18", cy: "5", r: "3", key: "gq8acd" }]
+];
+const BellDot = createLucideIcon("bell-dot", __iconNode);
+
+export { __iconNode, BellDot as default };
+//# sourceMappingURL=bell-dot.mjs.map