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/arrow-down-1-0.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: "m3 16 4 4 4-4", key: "1co6wj" }],
+  ["path", { d: "M7 20V4", key: "1yoxec" }],
+  ["path", { d: "M17 10V4h-2", key: "zcsr5x" }],
+  ["path", { d: "M15 10h4", key: "id2lce" }],
+  ["rect", { x: "15", y: "14", width: "4", height: "6", ry: "2", key: "33xykx" }]
+];
+const ArrowDown10 = createLucideIcon("arrow-down-1-0", __iconNode);
+
+export { __iconNode, ArrowDown10 as default };
+//# sourceMappingURL=arrow-down-1-0.mjs.map