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/grip-horizontal.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 = [
+  ["circle", { cx: "12", cy: "9", r: "1", key: "124mty" }],
+  ["circle", { cx: "19", cy: "9", r: "1", key: "1ruzo2" }],
+  ["circle", { cx: "5", cy: "9", r: "1", key: "1a8b28" }],
+  ["circle", { cx: "12", cy: "15", r: "1", key: "1e56xg" }],
+  ["circle", { cx: "19", cy: "15", r: "1", key: "1a92ep" }],
+  ["circle", { cx: "5", cy: "15", r: "1", key: "5r1jwy" }]
+];
+const GripHorizontal = createLucideIcon("grip-horizontal", __iconNode);
+
+export { __iconNode, GripHorizontal as default };
+//# sourceMappingURL=grip-horizontal.mjs.map