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/decimals-arrow-left.mjs

@@ -0,0 +1,19 @@
+/**
+ * @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 21-3-3 3-3", key: "s3o1nf" }],
+  ["path", { d: "M20 18H10", key: "14r3mt" }],
+  ["path", { d: "M3 11h.01", key: "1eifu7" }],
+  ["rect", { x: "6", y: "3", width: "5", height: "8", rx: "2.5", key: "v9paqo" }]
+];
+const DecimalsArrowLeft = createLucideIcon("decimals-arrow-left", __iconNode);
+
+export { __iconNode, DecimalsArrowLeft as default };
+//# sourceMappingURL=decimals-arrow-left.mjs.map